Question

A person is standing on a truck moving with 14.7 ms^-1 on a horizontal road. He throws a ball so that it returns to him when the truck has moved 58.8 m. Find the speed of the ball and angle of projection as seen by a man standing on the road.

• A. 22.5 ms^-1, 53⁰
• B. 24.5 ms^-1, 53⁰
• C. 19.6 ms^-1, vertical
• D. None of these

Answer 1

Answer: (B)

24.5 ms^-1, 53⁰

Answer 2

T = $\frac{58.8}{14.7} = 4s$

T = $\frac{2u_{y}}{g} = 4$ ∴ u_y = 19.6 ms^-1

v = $\sqrt{14.7^{2} + 19.6^{2}}$ = 24.5 ms^-1

tan β = $\frac{v_{y}}{v_{x}} = \frac{19.6}{14.7} = \frac{4}{3}$ or β = 53⁰ wrt horizontal.