Speed definition – Speed is defined as the rate at which a particle covers a distance along a given path. It is given by the ratio of distance travelled to the time taken.
Speed formula – Distance travelled (s)/Time (t)
- Since distance travelled is a scalar, the speed of a particle is also a scalar.
- The unit of speed is cm s-1 in C.G.S. system and m s-1 in M.KS. or S.I. system.
The speed of a particle at a given instant is known as instantaneous speed. The speedometer of a vehicle indicates the instantaneous speed of the vehicle.
Uniform Speed: A body or particle is said to possess uniform speed if it travels equal distances in equal intervals of time.
Consider a person travelling from A to B through O. If he walks at a constant rate of 1 m s-1 , i.e., for every 1 s if he travels 1 m, then the person is said to possess uniform speed. Uniform speed indicates that the instantaneous speed of particle remains the same throughout the motion.
Variable speed: If the instantaneous speed of a particle changes with time, then the body is said to be moving with variable speed.
Average speed: Defined as the ratio of the total distance travelled to the total time taken by the particle to cover that distance.
Average speed formula = Total distance/Total time
Velocity: It is displacement of a body in unit time or rate of displacement.
Velocity formula = displacement/time
Velocity is a vector quantity. SI unit of velocity is m s-1 and or C.G.S. unit of velocity is cm s-1 .