Question

1. A body is thrown from height of 200 m at 15 m/s. Find the time required for the body to strike the ground if its initial velocity directed 1) upwards, 2) downwards. Find the velocity with which it hits the ground ( g 10 m/s2 ). 2. The place of hitting the ground of the second stone thrown by a rock-climber from the top of a vertical rock is twice distant from the base of the rock than the place of the first hitting of the stone thrown from the intermediate height. What is the relationship between these heights? 3. A point is turning along the circular path with R = 10 m. When its normal acceleration is 4.9 m/s2 , the angle that total acceleration makes with the normal acceleration is 60o. Find 1) the linear and angular velocities, and 2) the tangential and angular accelerations.

Answer 1

ANSWER

When the ball reaches the highest point, its velocity will be zero. So final velocity is v=0m/s

Here, the time to reach highest point is equal to time to hit ground from highest point. 

Consider upward motion, the acceleration of the ball is a=−g=−9.8m/s2 (minus for motion opposite to gravity)

If t be the required time.

Using v=u+at,

0=25+(−9.8)t

⟹ t=2.5s

Thus the ball hits the ground after 2.5 seconds after reaching its highest point.