Formula for Velocity

If you are taking your first basic physics course, you are bound to come across the concept of ‘velocity’, which is one of the most fundamental concepts that you should understand. If you plan to go deep and really understand physics, you must question everything and grasp fundamental concepts quite deeply. Merely knowing the formula is not enough.

Displacement is the amount of change in position of an object, from one place to another, with reference to a fixed frame of reference. Let me explain this through an example. When you sit in a car and it starts moving, you are being moved or displaced from your position. Here, the frame of reference is the road as you are moving over it. So, displacement is the distance you cover, between your starting and ending point.

Velocity is the rate of displacement of the car, per unit time, in a particular direction.

How is Velocity Different From Speed?

Speed is a scalar quantity, while velocity is a vector quantity. That is, when I talk about the speed of a car, I don’t worry about which direction it’s going in. I only want to know the numerical measure of distance covered in unit time. On the other hand, while specifying velocity, I specify the direction.

Formula

The average velocity formula (in case ΔX is the displacement vector and ΔT is the time interval of displacement), is the following:

Velocity (V) = Displacement/Time = ΔX/ΔT

Thus, velocity is the rate of change of displacement, with time. This will be one of the many additions to your physics formulas list, which will keep growing, as you go deeper into the subject.

Considering you know elementary calculus, the instantaneous velocity of a moving object is given by the derivative of the displacement vector, with respect to time, and is given by:

Instantaneous Velocity = dX/dt

In this formula, X is a vector quantity and denotes the displacement. Calculus allows you to calculate the velocity at each instant of time and considers tiny increments in distance and time.

Units

Velocity is measured in Kilometers/hour. Depending on the units used for distance and time, you can have various units. In SI units, it is measured in meters per second, with the distance covered, measured in meters, and time in seconds.

Working through the velocity formula step by step is a solid first pass at motion forces and simple machines.