Question

1. A stone is thrown vertically upwards. During its journey to the top, when is it that both its velocity and its acceleration are equal to zero?

   1. Halfway on the way up.

   2. Halfway on the way down.

   3. At the top of the flight.

   4. Never – there is no instance when both of these quantities equal zero at the same time.

Answer 1

Never - there is no instance when both of these quantities equal zero at the same time.

Acceleration of the stone will always be equal to acceleration due to gravity , it will never be zero during the stones journey to the top whereas the velocity of the stone will be zero at the topmost point.

Answer 2

At the highest point of the stone's trajectory, its velocity is zero as it changes direction from moving upwards to moving downwards. At this point, the acceleration due to gravity is also zero as the stone momentarily stops moving vertically and starts to fall. Therefore, the correct answer is "At the top of the flight."