Question

Two equal forces are applied to a door. The first force is applied at the midpoint of the door;

Answer 1

Answer:

B

Explanation:

Torque exerted on an object depends upon three things.

1. Moment arm

2. Magnitude of applied force

3. Direction of force

T=r x F

T= r * F sinФ

Let T1 is force due to force applied at mid point of door.

let d is the width of door, so

T1= $\frac{d}{2}* F * sin(90$°)                  (∴ moment arm =d)

T1=$\frac{d* F}{2}$  __________(2)       (∴ sin 90°=1)

Let T2 is the torque due to force applied at the doorknob.

T2=  $d* F * sin(90)$                                (∴ moment arm =d)

T2=$d*F$ __________(2)                      (∴ sin 90°=1)

From equation (1) and equation (2)

2T1=T2

or

T1= T2/2

As T2 is greater so option B is the correct answer.