Question

Give an example of a motion in which average velocity is zero,but the average speed is not zero

Answer 1

It is true for most of the cases bot not always. So the answer is False. What is velocity ? It is the rate of change of displacement. Velocity being a vector quantity has both magnitude and direction. There can be a case when the magnitude is constant but direction varies and here is the catch in the question. Suppose an object is moving round the circle with velocity whose magnitude is constant. Now the average velocity of the object during the whole revolution is 0 because the net displacement is 0 but the object is accelerating because the direction is changing continuously. Another very common example is throwing of an object in the air. When the object reaches its highest point, then its velocity is 0 for a particular instant when it changes its direction but the object is still accelerating at a constant g=9.8 m/s.