Speed formula - Distance travelled (s)/Time (t) Unit of speed SI unit of speed is m s -1 CGS unit is cm s -1 Since distance travelled is a scalar, the speed of a particle is also a scalar. Instantaneous Speed 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 Average speed : Defined as the ra...