Physics is the most fundamental of all sciences. It is also one of the toughest sciences to master. Learning physics is basically studying the fundamental laws that govern our universe. I would say that there is a lot more to ascertain than just remember and mug up the physics formulas. Try to understand what a formula says and means, and what physical relation it expounds. If you understand the physical concepts underlying those formulas, deriving them or remembering them is easy. This Buzzle article lists some physics formulas that you would need in solving basic physics problems.
Physics Formulas
Mechanics is the oldest branch of physics. Mechanics deals with all kinds and complexities of motion. It includes various techniques, which can simplify the solution of a mechanical problem.
Motion in One Dimension
The formulas for motion in one dimension (Also called Kinematical equations of motion) are as follows. (Here 'u' is initial velocity, 'v' is final velocity, 'a' is acceleration and t is time):
Formulas for momentum, impulse and force concerning a particle moving in 3 dimensions are as follows (Here force, momentum and velocity are vectors ):
Pressure is defined as force per unit area:
Density
Density is the mass contained in a body per unit volume.
The formula for density is:
Angular Momentum
Angular momentum is an analogous quantity to linear momentum in which the body is undergoing rotational motion. The formula for angular momentum (J) is given by:
J = r x p
where J denotes angular momentum, r is radius vector and p is linear momentum.
Torque
Torque can be defined as moment of force. Torque causes rotational motion. The formula for torque is: τ = r x F, where τ is torque, r is the radius vector and F is linear force.
Circular Motion
The formulas for circular motion of an object of mass 'm' moving in a circle of radius 'r' at a tangential velocity 'v' are as follows:
Center of Mass
General Formula for Center of mass of a rigid body is :
where R is the position vector for center of mass, r is the generic position vector for all the particles of the object and N is the total number of particles.
Reduced Mass for two Interacting Bodies
The physics formula for reduced mass (μ) is :
where m_{1} is mass of the first body, m_{2} is the mass of the second body.
Work and Energy
Formulas for work and energy in case of one dimensional motion are as follows:
W (Work Done) = F (Force) x D (Displacement)
Energy can be broadly classified into two types, Potential Energy and Kinetic Energy. In case of gravitational force, the potential energy is given by
P.E.(Gravitational) = m (Mass) x g (Acceleration due to Gravity) x h (Height)
The transitional kinetic energy is given by ½ m (mass) x v^{2}(velocity squared)
Power
Power is, work done per unit time. The formula for power is given as
where P=power, W = Work, t = time.
Friction can be classified to be of two kinds : Static friction and dynamic friction.
Static Friction: Static friction is characterized by a coefficient of static friction μ . Coefficient of static friction is defined as the ratio of applied tangential force (F) which can induce sliding, to the normal force between surfaces in contact with each other. The formula to calculate this static coefficient is as follows:
The amount of force required to slide a solid resting on flat surface depends on the co efficient of static friction and is given by the formula:
F_{Horizontal} = μ x M(Mass of solid) x g (acceleration)
Dynamic Friction:
Dynamic friction is also characterized by the same coefficient of friction as static friction and therefore formula for calculating coefficient of dynamic friction is also the same as above. Only the dynamic friction coefficient is generally lower than the static one as the applied force required to overcome normal force is lesser.
Here are some formulas for Moments of Inertia of different objects. (M stands for mass, R for radius and L for length):
Here are some important formulas, related to Newtonian Gravity:
Newton's Law of universal Gravitation:
where
Here are two important formulas related to projectile motion:
(v = velocity of particle, v_{0} = initial velocity, g is acceleration due to gravity, θ is angle of projection, h is maximum height and l is the range of the projectile.)
Horizontal range of projectile (l) = v_{0} ^{2}sin 2θ / g
The physics formula for the period of a simple pendulum (T) = 2π √(l/g)where
The Period of a conical pendulum (T) = 2π √(lcosθ/g)
where
Here are some formulas related to electricity.
Ohm's Law
Ohm's law gives a relation between the voltage applied a current flowing across a solid conductor:
V (Voltage) = I (Current) x R (Resistance)
Power
In case of a closed electrical circuit with applied voltage V and resistance R, through which current I is flowing,
= I^{2}R. . . (because V = IR, Ohm's Law)
Kirchoff's Voltage Law
For every loop in an electrical circuit:
Σ_{i}V_{i} = 0
where V_{i} are all the voltages applied across the circuit.
Kirchoff's Current Law
At every node of an electrical circuit:
Σ_{i}I_{i} = 0
where I_{i} are all the currents flowing towards or away from the node in the circuit.
Resistance
The physics formulas for equivalent resistance in case of parallel and series combination are as follows:
Resistances R_{1}, R_{2}, R_{3} in series:
R_{eq} = R_{1} + R_{2} + R_{3}
Resistances R_{1} and R_{2} in parallel:
For n number of resistors, R_{1}, R_{2}...R_{n}, the formula will be:
1/R_{eq} = 1/R_{1} + 1/R_{2} + 1/R_{3}...+ 1/R_{n}
Capacitors
A capacitor stores electrical energy, when placed in an electric field. A typical capacitor consists of two conductors separated by a dielectric or insulating material. Here are the most important formulas related to capacitors. Unit of capacitance is Farad (F) and its values are generally specified in mF (micro Farad = 10 ^{6} F).
Capacitance (C) = Q / V
Energy Stored in a Capacitor (E_{cap}) = 1/2 CV^{2} = 1/2 (Q^{2} / C) = 1/2 (QV)
Current Flowing Through a Capacitor I = C (dV / dt)
Equivalent capacitance for 'n' capacitors connected in parallel:
C_{eq} (Parallel) = C_{1} + C_{2} + C_{3}...+ C_{n} = Σ_{i=1 to n} C_{i}
Equivalent capacitance for 'n' capacitors in series:
1 / C_{eq} (Series) = 1 / C_{1} + 1 / C_{2}...+ 1 / C_{n} = Σ_{i=1 to n} (1 / C_{i})
Here
C = kε_{0} (A/d)
Where
C = 2π kε_{0} [L / ln(b / a)]
Where
C = 4π kε_{0} [(ab)/(ba)]
Where
An inductor is an electrical component which resists the flow of electrons or electric current through it. This property of inductance, in these devices, is caused by the electromotive force, created by magnetic field induced in them. The unit of inductance is Henry. Here are some important formulas associated with inductors.
Energy Stored in Inductor (E_{stored}) = 1/2 (LI^{2})
Where, L is inductance and I is the current flowing through the inductor.
Inductance of a cylindrical air core Coil (L) = (m_{0}KN^{2}A / l)
Where
For inductors, L_{1}, L_{2}...L_{n} connected in series,
L_{eq} = L_{1} + L_{2}...+ L_{n} (L is inductance)
Inductors in a Parallel Network
For inductors, L_{1}, L_{2}...L_{n} connected in parallel,
1 / L_{eq} = 1 / L_{1} + 1 / L_{2}...+ 1 / L_{n}
Thermodynamics is a vast field providing an analysis of the behavior of matter in bulk. It's a field focused on studying matter and energy in all their manifestations. Here are some of the most important formulas associated with classical thermodynamics and statistical physics.
First Law of Thermodynamics
dU = dQ + dW
where, dU is the change in internal energy, dQ is the heat absorbed by the system and dW is the work done on the system.
Thermodynamic Potentials
All of thermodynamical phenomena can be understood in terms of the changes in five thermodynamic potentials under various physical constraints. They are Internal Energy (U), Enthalpy (H), Helmholtz Free Energy (F), Gibbs Free Energy (G), Landau or Grand Potential (Φ). Each of these scalar quantities represents the potentiality of a thermodynamic system to do work of various kinds under different types of constraints on its physical parameters.
Ideal Gas Equations
An ideal gas is a physicist's conception of a perfect gas composed of noninteracting particles which are easier to analyze, compared to real gases, which are much more complex, consisting of interacting particles. The resulting equations and laws of an ideal gas conform with the nature of real gases under certain conditions, though they fail to make exact predictions due the interactivity of molecules, which is not taken into consideration. Here are some of the most important physics formulas and equations, associated with ideal gases. Let's begin with the prime ideal gas laws and the equation of state of an ideal gas.
Kinetic Theory of Gases
Based on the primary assumptions that the volume of atoms or molecules is negligible, compared to the container volume and the attractive forces between molecules are negligible, the kinetic theory describes the properties of ideal gases. Here are the most important physics formulas related to the kinetic theory of monatomic gases.
Pressure (P) = 1/3 (Nm v^{2})
Here, P is pressure, N is the number of molecules and v^{2} is the mean squared particle velocity.
Internal Energy (U) = 3/2 (NkT)
Heat Capacities
Heat Capacity at Constant Pressure (C_{p}) = 5/2 Nk = C_{v} + Nk
Heat Capacity at Constant Volume (C_{v}) = 3/2 Nk
Ratio of Heat Capacities (γ) = C_{p} / C_{v} = 5/3
Velocity Formulas
Mean Molecular Velocity (V_{mean}) = [(8kT)/(πm)]^{1/2}
Root Mean Square Velocity of a Molecule (V_{rms}) = (3kT/m)^{1/2}
Most Probable Velocity of a Molecule (V_{prob}) = (2kT/m)^{1/2}
Mean Free Path of a Molecule (λ) = (kT)/√2πd^{2}P (Here P is in Pascals)
Here N is the number of molecules, k is the Boltzmann constant, P is pressure, d is the molecular diameter, m is mass of the molecule and T is the gas temperature.
Here are some of the basic formulas from electromagnetism.
The coulombic force between two charges at rest is
Here,
The Lorentz force is the force exerted by an electric and/or magnetic field on a charged particle.
(Lorentz Force) F = q (E + v x B)
where
Here are some of the most important relativistic mechanics formulas. The transition from classical to relativistic mechanics is not at all smooth, as it merges space and time into one by taking away the Newtonian idea of absolute time. If you know what is Einstein's special theory of relativity, then the following formulas will make sense to you.
Lorentz Transformations
Lorentz transformations can be perceived as rotations in four dimensional space. Just as rotations in 3D space mixes the space coordinates, a Lorentz transformation mixes time and space coordinates. Consider two, three dimensional frames of reference S(x,y,z) and S'(x',y',z') coinciding with each other.
Now consider that frame S' starts moving with a constant velocity v with respect to S frame. In relativistic mechanics, time is relative! So the time coordinate for the S' frame will be t' while that for S frame will be t.
Consider
The coordinate transformations between the two frames are known as Lorentz transformations and are given as follows:
Lorentz Transformations of Space and Time
x = γ (x' + vt') and x' = γ (x  vt)
y = y'
z= z'
t = γ(t' + vx'/c^{2}) and t' = γ(t  vx/c^{2})
Relativistic Velocity Transformations
In the same two frames S and S', the transformations for velocity components will be as follows (Here (U_{x}, U_{y}, U_{z}) and (U_{x}', U_{y}', U_{z}') are the velocity components in S and S' frames respectively):
U_{x} = (U_{x}' + v) / (1 + U_{x}'v / c^{2})
U_{y} = (U_{y}') / γ(1 + U_{x}'v / c^{2})
U_{z} = (U_{z}') / γ(1 + U_{x}'v / c^{2}) and
U_{x}' = (U_{x}  v) / (1  U_{x}v / c^{2})
U_{y}' = (U_{y}) / γ(1  U_{x}v / c^{2})
U_{z}' = (U_{z}) / γ(1  U_{x}v / c^{2})
Momentum and Energy Transformations in Relativistic Mechanics
Consider the same two frames (S, S') as in case of Lorentz coordinate transformations above. S' is moving at a velocity 'v' along the xaxis. Here again γis the Lorentz factor. In S frame (P_{x}, P_{y}, P_{z}) and in S' frame (P_{x}', P_{y}', P_{z}') are momentum components. Now we consider formulas for momentum and energy transformations for a particle, between these two reference frames in relativistic regime.
Component wise Momentum Transformations and Energy Transformations
P_{x} = γ(P_{x}' + vE' / c^{2})
P_{y} = P_{y}'
P_{z} = P_{z}'
E = γ(E' + vP_{x})
and
P_{x}' = γ(P_{x}  vE' / c^{2})
P_{y}' = P_{y}
P_{z}' = P_{z}
E' = γ(E  vP_{x})
Physical Formulas for Quantities in Relativistic Dynamics
All the known quantities in classical mechanics get modified, when we switch over to relativistic mechanics which is based on the special theory of relativity. Here are formulas of quantities in relativistic dynamics.
Relativistic momentum p = γm_{0}v
where m_{0} is the rest mass of the particle.
Rest mass energy E = m_{0}c^{2}
Total Energy (Relativistic) E = √(p^{2}c^{2} + m_{0}^{2}c^{4}))
Optics is one of the oldest branches of physics. There are many important optics physics formulas, which we need frequently in solving physics problems. Here are some of the important and frequently needed optics formulas.
Snell's Law
where
The most fundamental property of any optical lens is its ability to converge or diverge rays of light, which is measued by its focal length. Here is the lens maker's formula, which can help you calculate the focal length of a lens, from its physical parameters.
1 / f = [n1][(1 / R_{1})  (1 / R_{2}) + (n1) d / nR_{1}R_{2})]
Here,
(Thin Lens Approximation) 1 / f ≈ (n1) [1 / R_{1}  1 / R_{2}]
Compound Lenses
The combined focal length (f) of two thin lenses, with focal length f_{1} and f_{2}, in contact with each other:
1 / f = 1 / f_{1} + 1 / f_{2}
If the two thin lenses are separated by distance d, their combined focal length is provided by the formula:
1 / f = 1 / f_{1} + 1 / f_{2}  (d / f_{1}  f_{2}))
Newton's Rings Formulas
Here are the important formulas for Newton's rings experiment which illustrates diffraction.
n^{th} Dark ring formula: r^{2}_{n} = nRλ
n^{th} Bright ring formula: r^{2}_{n} = (n + ½) Rλ
where
Quantum physics is one of the most interesting branches of physics, which describes atoms and molecules, as well as atomic substructure. Here are some of the formulas related to the very basics of quantum physics, that you may require frequently.
De Broglie Wave
De Broglie Wavelength:
where, λ De Broglie Wavelength, h  Planck's Constant, p is momentum of the particle.
Bragg's Law of Diffraction: 2a Sin θ = nλ
where
The plank relation gives the connection between energy and frequency of an electromagnetic wave:
where h is Planck's Constant, v the frequency of radiation and ω = 2πv
Uncertainty Principle
Uncertainty principle is the bedrock on which quantum mechanics is based. It exposes the inherent limitation that nature imposes on how precisely a physical quantity can be measured. Uncertainty relation holds between any two noncommuting variables. Two of the special uncertainty relations are given below.
PositionMomentum Uncertainty
What the positionmomentum uncertainty relation says is, you cannot predict where a particle is and how fast it is moving, both, with arbitrary accuracy. The more precise you are about the position, more uncertain will you be about the particle's momentum and vice versa. The mathematical statement of this relation is given as follows:
where Δx is the uncertainty in position and Δp is the uncertainty in momentum.
EnergyTime Uncertainty
This is an uncertainty relation between energy and time. This relation gives rise to some astounding results like, creation of virtual particles for arbitrarily short periods of time! It is mathematically stated as follows:
where ΔE is the uncertainty in energy and Δt is the uncertainty in time.
This concludes my review of some of the important physics formulas. This list, is only representative and is by no means anywhere near complete. Physics is the basis of all sciences and therefore its domain extends over all sciences. Every branch of physics theory abounds with countless formulas. If you resort to just mugging up all these formulas, you may pass exams, but you will not be doing real physics. If you grasp the underlying theory behind these formulas, physics will be simplified. To view physics through the formulas and laws, you must be good at maths. There is no way you can run away from it. Mathematics is the language of nature!
The more things we find out about nature, more words we need to describe them. This has led to increasing jargonization of science with fields and subfields getting generated. You could refer to a glossary of science terms and scientific definitions for any jargon that is beyond your comprehension.
If you really want to get a hang of what it means to be a physicist and get an insight into physicist's view of things, read 'Feynman Lectures on Physics', which is highly recommended reading, for anyone who loves physics. It is written by one of the greatest physicists ever, Prof. Richard Feynman. Read and learn from the master. Solve as many problems as you can, on your own, to get a firm grasp of the subject.
Physics Formulas
 Mechanics
 Friction
 Moment of Inertia
 Newtonian Gravity
 Projectile Motion
 Simple Pendulum
 Electricity
 Thermodynamics
 Electromagnetism
 Optics
 Quantum Physics
Mechanics is the oldest branch of physics. Mechanics deals with all kinds and complexities of motion. It includes various techniques, which can simplify the solution of a mechanical problem.
Motion in One Dimension
The formulas for motion in one dimension (Also called Kinematical equations of motion) are as follows. (Here 'u' is initial velocity, 'v' is final velocity, 'a' is acceleration and t is time):
 s = ut + ½ at^{2}
 v = u + at
 v^{2} = u^{2} + 2as
 v_{av} (Average Velocity) = (v+u)/2
Formulas for momentum, impulse and force concerning a particle moving in 3 dimensions are as follows (Here force, momentum and velocity are vectors ):
 Momentum is the product of mass and velocity of a body. Momentum is calculate using the formula: P = m (mass) x v (velocity)
 Force can defined as something which causes a change in momentum of a body. Force is given by the celebrated newton's law of motion: F = m (mass) x a (acceleration)
 Impulse is a large force applied in a very short time period. The strike of a hammer is an impulse. Impulse is given by I = m(vu)
Pressure is defined as force per unit area:
Pressure (P) =  Force (F) Area (A) 
Density
Density is the mass contained in a body per unit volume.
The formula for density is:
Density (D) =  Mass(M) Volume (V) 
Angular Momentum
Angular momentum is an analogous quantity to linear momentum in which the body is undergoing rotational motion. The formula for angular momentum (J) is given by:
J = r x p
where J denotes angular momentum, r is radius vector and p is linear momentum.
Torque
Torque can be defined as moment of force. Torque causes rotational motion. The formula for torque is: τ = r x F, where τ is torque, r is the radius vector and F is linear force.
Circular Motion
The formulas for circular motion of an object of mass 'm' moving in a circle of radius 'r' at a tangential velocity 'v' are as follows:
Centripetal force (F) =  mv^{2} r 
Centripetal Acceleration (a) =  v^{2} r 
Center of Mass
General Formula for Center of mass of a rigid body is :
R =  Σ^{N}_{i = 1} m_{i}r_{i} Σ^{N}_{i = 1}m_{i} 
where R is the position vector for center of mass, r is the generic position vector for all the particles of the object and N is the total number of particles.
Reduced Mass for two Interacting Bodies
The physics formula for reduced mass (μ) is :
μ =  m_{1}m_{2} m_{1} + m_{2} 
Work and Energy
Formulas for work and energy in case of one dimensional motion are as follows:
W (Work Done) = F (Force) x D (Displacement)
Energy can be broadly classified into two types, Potential Energy and Kinetic Energy. In case of gravitational force, the potential energy is given by
P.E.(Gravitational) = m (Mass) x g (Acceleration due to Gravity) x h (Height)
The transitional kinetic energy is given by ½ m (mass) x v^{2}(velocity squared)
Power
Power is, work done per unit time. The formula for power is given as
Power (P) =  V^{2} R  =I^{2}R 
[Back to Formula Index]
Friction can be classified to be of two kinds : Static friction and dynamic friction.
Static Friction: Static friction is characterized by a coefficient of static friction μ . Coefficient of static friction is defined as the ratio of applied tangential force (F) which can induce sliding, to the normal force between surfaces in contact with each other. The formula to calculate this static coefficient is as follows:
μ =  Applied Tangential Force (F) Normal Force(N) 
The amount of force required to slide a solid resting on flat surface depends on the co efficient of static friction and is given by the formula:
F_{Horizontal} = μ x M(Mass of solid) x g (acceleration)
Dynamic Friction:
Dynamic friction is also characterized by the same coefficient of friction as static friction and therefore formula for calculating coefficient of dynamic friction is also the same as above. Only the dynamic friction coefficient is generally lower than the static one as the applied force required to overcome normal force is lesser.
[Back to Formula Index]
Here are some formulas for Moments of Inertia of different objects. (M stands for mass, R for radius and L for length):
Object  Axis  Moment of Inertia 
Disk  Axis parallel to disc, passing through the center  MR^{2}/2 
Disk  Axis passing through the center and perpendicular to disc  MR^{2}/2 
Thin Rod  Axis perpendicular to the Rod and passing through center  ML^{2}/12 
Solid Sphere  Axis passing through the center  2MR^{2}/5 
Solid Shell  Axis passing through the center  2MR^{2}/3 
[Back to Formula Index]
Here are some important formulas, related to Newtonian Gravity:
Newton's Law of universal Gravitation:
F_{g} =  Gm_{1}m_{2} r^{2} 
 m_{1}, m_{2} are the masses of two bodies
 G is the universal gravitational constant which has a value of 6.67300 × 1011 m3 kg1 s2
 r is distance between the two bodies
 M is mass of central gravitating body
 R is radius of the central body
[Back to Formula Index]
Here are two important formulas related to projectile motion:
(v = velocity of particle, v_{0} = initial velocity, g is acceleration due to gravity, θ is angle of projection, h is maximum height and l is the range of the projectile.)
Maximum height of projectile (h) =  v_{0} ^{2}sin^{2}θ 2g 
Horizontal range of projectile (l) = v_{0} ^{2}sin 2θ / g
[Back to Formula Index]
The physics formula for the period of a simple pendulum (T) = 2π √(l/g)where
 l is the length of the pendulum
 g is acceleration due to gravity
The Period of a conical pendulum (T) = 2π √(lcosθ/g)
where
 l is the length of the pendulum
 g is acceleration due to gravity
 Half angle of the conical pendulum
[Back to Formula Index]
Here are some formulas related to electricity.
Ohm's Law
Ohm's law gives a relation between the voltage applied a current flowing across a solid conductor:
V (Voltage) = I (Current) x R (Resistance)
Power
In case of a closed electrical circuit with applied voltage V and resistance R, through which current I is flowing,
Power (P) =  V^{2} R 
= I^{2}R. . . (because V = IR, Ohm's Law)
Kirchoff's Voltage Law
For every loop in an electrical circuit:
Σ_{i}V_{i} = 0
where V_{i} are all the voltages applied across the circuit.
Kirchoff's Current Law
At every node of an electrical circuit:
Σ_{i}I_{i} = 0
where I_{i} are all the currents flowing towards or away from the node in the circuit.
Resistance
The physics formulas for equivalent resistance in case of parallel and series combination are as follows:
Resistances R_{1}, R_{2}, R_{3} in series:
R_{eq} = R_{1} + R_{2} + R_{3}
Resistances R_{1} and R_{2} in parallel:
R_{eq} =  R_{1}R_{2} R_{1} + R_{2} 
For n number of resistors, R_{1}, R_{2}...R_{n}, the formula will be:
1/R_{eq} = 1/R_{1} + 1/R_{2} + 1/R_{3}...+ 1/R_{n}
Capacitors
A capacitor stores electrical energy, when placed in an electric field. A typical capacitor consists of two conductors separated by a dielectric or insulating material. Here are the most important formulas related to capacitors. Unit of capacitance is Farad (F) and its values are generally specified in mF (micro Farad = 10 ^{6} F).
Capacitance (C) = Q / V
Energy Stored in a Capacitor (E_{cap}) = 1/2 CV^{2} = 1/2 (Q^{2} / C) = 1/2 (QV)
Current Flowing Through a Capacitor I = C (dV / dt)
Equivalent capacitance for 'n' capacitors connected in parallel:
C_{eq} (Parallel) = C_{1} + C_{2} + C_{3}...+ C_{n} = Σ_{i=1 to n} C_{i}
Equivalent capacitance for 'n' capacitors in series:
1 / C_{eq} (Series) = 1 / C_{1} + 1 / C_{2}...+ 1 / C_{n} = Σ_{i=1 to n} (1 / C_{i})
Here
 C is the capacitance
 Q is the charge stored on each conductor in the capacitor
 V is the potential difference across the capacitor
C = kε_{0} (A/d)
Where
 k = dielectric constant (k = 1 in vacuum)
 ε_{0} = Permittivity of Free Space (= 8.85 × 10^{12} C^{2} / Nm^{2})
 A = Plate Area (in square meters)
 d = Plate Separation (in meters)
C = 2π kε_{0} [L / ln(b / a)]
Where
 k = dielectric constant (k = 1 in vacuum)
 ε_{0} = Permittivity of Free Space (= 8.85 × 10^{12} C^{2} / Nm^{2})
 L = Capacitor Length
 a = Inner conductor radius
 b = Outer conductor radius
C = 4π kε_{0} [(ab)/(ba)]
Where
 k = dielectric constant (k = 1 in vacuum)
 ε_{0} = Permittivity of Free Space (= 8.85 × 10^{12} C^{2} / Nm^{2})
 a = Inner conductor radius
 b = Outer conductor radius
An inductor is an electrical component which resists the flow of electrons or electric current through it. This property of inductance, in these devices, is caused by the electromotive force, created by magnetic field induced in them. The unit of inductance is Henry. Here are some important formulas associated with inductors.
Energy Stored in Inductor (E_{stored}) = 1/2 (LI^{2})
Where, L is inductance and I is the current flowing through the inductor.
Inductance of a cylindrical air core Coil (L) = (m_{0}KN^{2}A / l)
Where
 L is inductance measured in Henries
 N is the number of turns on the coil
 A is crosssectional area of the coil
 m_{0} is the permeability of free space (= 4π × 10^{7} H/m)
 K is the Nagaoka coefficient
 l is the length of coil
For inductors, L_{1}, L_{2}...L_{n} connected in series,
L_{eq} = L_{1} + L_{2}...+ L_{n} (L is inductance)
Inductors in a Parallel Network
For inductors, L_{1}, L_{2}...L_{n} connected in parallel,
1 / L_{eq} = 1 / L_{1} + 1 / L_{2}...+ 1 / L_{n}
[Back to Formula Index]
Thermodynamics is a vast field providing an analysis of the behavior of matter in bulk. It's a field focused on studying matter and energy in all their manifestations. Here are some of the most important formulas associated with classical thermodynamics and statistical physics.
First Law of Thermodynamics
dU = dQ + dW
where, dU is the change in internal energy, dQ is the heat absorbed by the system and dW is the work done on the system.
Thermodynamic Potentials
All of thermodynamical phenomena can be understood in terms of the changes in five thermodynamic potentials under various physical constraints. They are Internal Energy (U), Enthalpy (H), Helmholtz Free Energy (F), Gibbs Free Energy (G), Landau or Grand Potential (Φ). Each of these scalar quantities represents the potentiality of a thermodynamic system to do work of various kinds under different types of constraints on its physical parameters.
Thermodynamic Potential  Defining Equation 

Internal Energy (U)  dU = TdS − pdV + µdN  
Enthalpy (H)  H = U + pV dH = TdS + Vdp + µdN  
Gibbs Free Energy (G)  G = U  TS + pV = F + pV = H  TS dG = SdT + Vdp + µdN  
Helmholtz Free Energy (F)  F = U  TS dF =  SdT  pdV + µdN  
Landau or Grand Potential  Φ = F  µN dΦ =  SdT  pdV  Ndµ 
Ideal Gas Equations
An ideal gas is a physicist's conception of a perfect gas composed of noninteracting particles which are easier to analyze, compared to real gases, which are much more complex, consisting of interacting particles. The resulting equations and laws of an ideal gas conform with the nature of real gases under certain conditions, though they fail to make exact predictions due the interactivity of molecules, which is not taken into consideration. Here are some of the most important physics formulas and equations, associated with ideal gases. Let's begin with the prime ideal gas laws and the equation of state of an ideal gas.
Law  Equation 

Boyle's Law  PV = Constant or P_{1}V_{1} = P_{2}V_{2} (At Constant Temperature)  
Charles's Law  V / T = Constant or V_{1} / T_{1} = V_{2} / T_{2} (At Constant Pressure)  
Amontons' Law of PressureTemperature  P / T = Constant or P_{1} / T_{1} = P_{2} / T_{2} (At Constant Volume)  
Equation of State For An Ideal Gas  PV = nRT = NkT 
Kinetic Theory of Gases
Based on the primary assumptions that the volume of atoms or molecules is negligible, compared to the container volume and the attractive forces between molecules are negligible, the kinetic theory describes the properties of ideal gases. Here are the most important physics formulas related to the kinetic theory of monatomic gases.
Pressure (P) = 1/3 (Nm v^{2})
Here, P is pressure, N is the number of molecules and v^{2} is the mean squared particle velocity.
Internal Energy (U) = 3/2 (NkT)
Heat Capacities
Heat Capacity at Constant Pressure (C_{p}) = 5/2 Nk = C_{v} + Nk
Heat Capacity at Constant Volume (C_{v}) = 3/2 Nk
Ratio of Heat Capacities (γ) = C_{p} / C_{v} = 5/3
Velocity Formulas
Mean Molecular Velocity (V_{mean}) = [(8kT)/(πm)]^{1/2}
Root Mean Square Velocity of a Molecule (V_{rms}) = (3kT/m)^{1/2}
Most Probable Velocity of a Molecule (V_{prob}) = (2kT/m)^{1/2}
Mean Free Path of a Molecule (λ) = (kT)/√2πd^{2}P (Here P is in Pascals)
Here N is the number of molecules, k is the Boltzmann constant, P is pressure, d is the molecular diameter, m is mass of the molecule and T is the gas temperature.
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Here are some of the basic formulas from electromagnetism.
The coulombic force between two charges at rest is
(F) =  q_{1}q_{2} 4πε_{0}r^{2} 
 q_{1}, q_{2} are charges
 ε_{0} is the permittivity of free space
 r is the distance between the two charges
The Lorentz force is the force exerted by an electric and/or magnetic field on a charged particle.
(Lorentz Force) F = q (E + v x B)
where
 q is the charge on the particle
 E and B are the electric and magnetic field vectors
Here are some of the most important relativistic mechanics formulas. The transition from classical to relativistic mechanics is not at all smooth, as it merges space and time into one by taking away the Newtonian idea of absolute time. If you know what is Einstein's special theory of relativity, then the following formulas will make sense to you.
Lorentz Transformations
Lorentz transformations can be perceived as rotations in four dimensional space. Just as rotations in 3D space mixes the space coordinates, a Lorentz transformation mixes time and space coordinates. Consider two, three dimensional frames of reference S(x,y,z) and S'(x',y',z') coinciding with each other.
Now consider that frame S' starts moving with a constant velocity v with respect to S frame. In relativistic mechanics, time is relative! So the time coordinate for the S' frame will be t' while that for S frame will be t.
Consider
γ =  1 √(1  v^{2}/c^{2}) 
The coordinate transformations between the two frames are known as Lorentz transformations and are given as follows:
Lorentz Transformations of Space and Time
x = γ (x' + vt') and x' = γ (x  vt)
y = y'
z= z'
t = γ(t' + vx'/c^{2}) and t' = γ(t  vx/c^{2})
Relativistic Velocity Transformations
In the same two frames S and S', the transformations for velocity components will be as follows (Here (U_{x}, U_{y}, U_{z}) and (U_{x}', U_{y}', U_{z}') are the velocity components in S and S' frames respectively):
U_{x} = (U_{x}' + v) / (1 + U_{x}'v / c^{2})
U_{y} = (U_{y}') / γ(1 + U_{x}'v / c^{2})
U_{z} = (U_{z}') / γ(1 + U_{x}'v / c^{2}) and
U_{x}' = (U_{x}  v) / (1  U_{x}v / c^{2})
U_{y}' = (U_{y}) / γ(1  U_{x}v / c^{2})
U_{z}' = (U_{z}) / γ(1  U_{x}v / c^{2})
Momentum and Energy Transformations in Relativistic Mechanics
Consider the same two frames (S, S') as in case of Lorentz coordinate transformations above. S' is moving at a velocity 'v' along the xaxis. Here again γis the Lorentz factor. In S frame (P_{x}, P_{y}, P_{z}) and in S' frame (P_{x}', P_{y}', P_{z}') are momentum components. Now we consider formulas for momentum and energy transformations for a particle, between these two reference frames in relativistic regime.
Component wise Momentum Transformations and Energy Transformations
P_{x} = γ(P_{x}' + vE' / c^{2})
P_{y} = P_{y}'
P_{z} = P_{z}'
E = γ(E' + vP_{x})
and
P_{x}' = γ(P_{x}  vE' / c^{2})
P_{y}' = P_{y}
P_{z}' = P_{z}
E' = γ(E  vP_{x})
Physical Formulas for Quantities in Relativistic Dynamics
All the known quantities in classical mechanics get modified, when we switch over to relativistic mechanics which is based on the special theory of relativity. Here are formulas of quantities in relativistic dynamics.
Relativistic momentum p = γm_{0}v
where m_{0} is the rest mass of the particle.
Rest mass energy E = m_{0}c^{2}
Total Energy (Relativistic) E = √(p^{2}c^{2} + m_{0}^{2}c^{4}))
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Optics is one of the oldest branches of physics. There are many important optics physics formulas, which we need frequently in solving physics problems. Here are some of the important and frequently needed optics formulas.
Snell's Law
Sin i Sin r  =  n_{2} n_{1}  =  v_{1} v_{2} 
 where i is angle of incidence
 r is the angle of refraction
 n_{1} is refractive index of medium 1
 n_{2} is refractive index of medium 2
 v_{1}, v_{2} are the velocities of light in medium 1 and medium 2 respectively
where
 u  object distance
 v  image distance
 f  Focal length of the lens
The most fundamental property of any optical lens is its ability to converge or diverge rays of light, which is measued by its focal length. Here is the lens maker's formula, which can help you calculate the focal length of a lens, from its physical parameters.
1 / f = [n1][(1 / R_{1})  (1 / R_{2}) + (n1) d / nR_{1}R_{2})]
Here,
 n is refractive index of the lens material
 R_{1} is the radius of curvature of the lens surface, facing the light source
 R_{2} is the radius of curvature of the lens surface, facing away from the light source
 d is the lens thickness
(Thin Lens Approximation) 1 / f ≈ (n1) [1 / R_{1}  1 / R_{2}]
Compound Lenses
The combined focal length (f) of two thin lenses, with focal length f_{1} and f_{2}, in contact with each other:
1 / f = 1 / f_{1} + 1 / f_{2}
If the two thin lenses are separated by distance d, their combined focal length is provided by the formula:
1 / f = 1 / f_{1} + 1 / f_{2}  (d / f_{1}  f_{2}))
Newton's Rings Formulas
Here are the important formulas for Newton's rings experiment which illustrates diffraction.
n^{th} Dark ring formula: r^{2}_{n} = nRλ
n^{th} Bright ring formula: r^{2}_{n} = (n + ½) Rλ
where
 n^{th} ring radius
 Radius of curvature of the lens
 Wavelength of incident light wave
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Quantum physics is one of the most interesting branches of physics, which describes atoms and molecules, as well as atomic substructure. Here are some of the formulas related to the very basics of quantum physics, that you may require frequently.
De Broglie Wave
De Broglie Wavelength:
λ =  h p 
where, λ De Broglie Wavelength, h  Planck's Constant, p is momentum of the particle.
Bragg's Law of Diffraction: 2a Sin θ = nλ
where
 a  Distance between atomic planes
 n  Order of Diffraction
 θ  Angle of Diffraction
 λ  Wavelength of incident radiation
The plank relation gives the connection between energy and frequency of an electromagnetic wave:
E = hv =  hω 2π 
where h is Planck's Constant, v the frequency of radiation and ω = 2πv
Uncertainty Principle
Uncertainty principle is the bedrock on which quantum mechanics is based. It exposes the inherent limitation that nature imposes on how precisely a physical quantity can be measured. Uncertainty relation holds between any two noncommuting variables. Two of the special uncertainty relations are given below.
PositionMomentum Uncertainty
What the positionmomentum uncertainty relation says is, you cannot predict where a particle is and how fast it is moving, both, with arbitrary accuracy. The more precise you are about the position, more uncertain will you be about the particle's momentum and vice versa. The mathematical statement of this relation is given as follows:
Δx.Δp ≥  h 2π 
where Δx is the uncertainty in position and Δp is the uncertainty in momentum.
EnergyTime Uncertainty
This is an uncertainty relation between energy and time. This relation gives rise to some astounding results like, creation of virtual particles for arbitrarily short periods of time! It is mathematically stated as follows:
ΔE.Δt ≥  h 2π 
where ΔE is the uncertainty in energy and Δt is the uncertainty in time.
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This concludes my review of some of the important physics formulas. This list, is only representative and is by no means anywhere near complete. Physics is the basis of all sciences and therefore its domain extends over all sciences. Every branch of physics theory abounds with countless formulas. If you resort to just mugging up all these formulas, you may pass exams, but you will not be doing real physics. If you grasp the underlying theory behind these formulas, physics will be simplified. To view physics through the formulas and laws, you must be good at maths. There is no way you can run away from it. Mathematics is the language of nature!
The more things we find out about nature, more words we need to describe them. This has led to increasing jargonization of science with fields and subfields getting generated. You could refer to a glossary of science terms and scientific definitions for any jargon that is beyond your comprehension.
If you really want to get a hang of what it means to be a physicist and get an insight into physicist's view of things, read 'Feynman Lectures on Physics', which is highly recommended reading, for anyone who loves physics. It is written by one of the greatest physicists ever, Prof. Richard Feynman. Read and learn from the master. Solve as many problems as you can, on your own, to get a firm grasp of the subject.