Q.41

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Found in: Page 332

### Physics for Scientists and Engineers: A Strategic Approach with Modern Physics

Book edition 4th
Author(s) Randall D. Knight
Pages 1240 pages
ISBN 9780133942651

# A kg ball on the end of a lightweight rod is located at where the axis is vertical. The other end of the rod is attached to a pivot at . What is the torque about the pivot? Write your answer using unit vectors.

Hence, the torque applied on the mass is

See the step by step solution

## Step : 1 Introduction

The rotating equivalent of force is torque. It is provided by.

The force is , and the distance between the pivot and the site of application of force is .

The right-hand thumb rule determines the direction of torque, which is a vector quantity.

## Step : 2 Explanation

For the application of force, see the diagram below:

## Step :3  Vector position

The position vector of the mass is:

Substitute for and for

On the mass, the force vector is:

Here, and are the mass and acceleration of the ball, respectively.

## Step : 4 Substituting

Substitute for

The torque acting on mass is

Substitute