Question

A ball is in free fall. Upwards is taken to be the positive direction. The vertical component of the displacement of the ball during a short time interval is _____ during ascent, and ___________ during descent.

• A. positive
• B. negative

Answer 1

Displacement:

• It is the change in the position of an object.
• It is a vector quantity.
• It can be positive, negative, and even zero.

Free Fall:

• A body is said to be in free fall if it is only acted upon by the acceleration due to gravity.
• There is no other force acting on the falling body
• For example, a stone dropped from the top of a building.

The displacement of the ball during a short interval of time:

• During ascent as the ball is going upwards, its position is positive.
• The velocity is decreasing but its direction is upwards i.e. positive.
• For example, Ball is moving under the effect of gravitational acceleration, which is always acting vertically downwards, so it is negative.

Thus, the vertical component of the displacement of the ball during a short time interval is positive during ascent, and negative during descent.