In everyday life we seldom find objects moving with a constant speed over long distances or for long durations of time. If the speed of an object moving along a straight line keeps changing, its motion is said to be non-uniform. On the other hand, an object moving along a straight line with a constant speed is said to be in uniform motion. In this case, the average speed is the same as the actual speed. Key Points You may have observed the motion of a vehicle on a straight road, march-past of soldiers in a parade, or the falling of a stone all these examples we see that the objects move along a straight line. A teacher should give the following examples of time and motion- The motion of your hands while running. The motion of a horse pulling a cart on a straight road. The motion of a child in a merry-go-round. The motion of a child on a see-saw. Motion of the hammer of an electric bell The motion of a train on a straight bridge. The motion of a cricket ball hit by a batsmen Thus from the above-mentioned points, it is clear that Motion of a boy sitting in a moving car in relation to the car is incorrect as the example of 'motion and time'. Hint The motion of a boy sitting in a moving car in relation to the car is not example of motion because in this situation boy remain stable with respect car.