Chapter 13, Problem 1IP

Why does a force directed through an axis of rotation not cause rotation at the axis?

Summary Introduction

To explain: The reason for a force which is directed through an axis of rotation did not cause rotation at the axis.

Concept introduction: The effect of rotation caused by applying a force on the object is known as torque. The torque can be found out using the magnitude of force and the length of moment arm.

Explanation of Solution

Write the equation to find the torque.

$T=F{d}_{\perp }$

Here, $T$ is the torque, $F$ is the force, $d_{\perp }$ is the moment arm.

When the force is directed through an axis of rotation, the value of moment arm is zero, thus, there will be no torque due to the force applied. Since, the force is not creating any torque; the force which is directed through an axis of rotation did not cause any rotation at the axis.