Speed & Velocity
- Speed: Distance travelled by the object in unit time.
- The SI unit of speed is metre per second. This is represented by the symbol m s–1 or m/s.
- Speed is a scalar quantity; it only has direction.
- Velocity: Velocity is the speed of an object moving in a definite direction.
- The SI unit of velocity is also metre per second.
- Velocity is a vector quantity; it has both magnitude and direction.
- In most cases, objects will be in non-uniform motion. Therefore, we describe the rate of motion of such objects in terms of ‘average’.
Example: Consider yourself going to a shop on a cycle, you stop cycle many times on the way and then you come from the shop to your home. Distance from shop to home = 3 km, time taken from home to shop = 1 hour and time taken from shop to home = 2 hour.
- Average speed = total distance / total time
= (3+3) / (1+2) = 2 km/hr
- Average velocity = displacement / total time
= (3-3) / (1+2) = 0 km/hr