Problem 22.

A ball is thrown vertically upward with a speed of 25.0m/s.

(a) How high does it rise?

(b) How long does it take to reach its highest point?

(c) How long does the ball take to hit the ground after it reaches its highest point?

(d) What is its velocity when it returns to the level from which it started?

Solution:

This is the motion with constant acceleration (free fall acceleration).

(a) We need to use the following equation (the initial velocity is 25 m/s and the final velocity is 0):

(b) We need to use the following equation (the initial velocity is 25 m/s and the final velocity is 0):

(c) At this moment we do not know the final velocity, but we know the initial velocity (it is 0) and we know the height (the traveled distance) – it is 31.9 m. Then we can use the following equation:

From this equation we can find time:

It is the same time as in part (b).

(d) Now we can find the final velocity (the magnitude):