Question

a ball is dropped from a building 45 m high simultaneously another ball is thrown up with a speed of 40m/s. calculate the relative speed of the balls with respect to time?

Answer 1

A ball is dropped from height of 45 m , this is the case of free fall.
$$\begin{gathered} velocityofballv=\sqrt{2gh}\left(h=45m\right) \\ v=\sqrt{2\times 10\times 45}=30m \end{gathered}$$

Relative speed between balls = 40+ 30 = 70 m/s