Chapter 5, Problem 7Q

To determine

A girl is whirling a ball on a string around her head in a horizontal plane. She wants to let go at precisely the right time so that the ball will hit a target on the other side of the yard. When should she let go of the string?

Answer to Problem 7Q

Solution:

She should let go of the string when the ball’s velocity direction should pass over the target because after that no horizontal force acting on the ball.

Explanation of Solution

Formula Used:

$\begin{array}{l}{\displaystyle \sum F_x=0}\end{array}$

$\begin{array}{l}{a}_x=0\end{array}$

When she let go of the string then in horizontal plane net force acting on the particle is zero hence it moves with the same velocity in a horizontal plane as during the leave of the string.

In vertical direction gravitational force is present so particle is accelerating downward with constant acceleration (g)