# Torque exerted on trap door by rope

1. Nov 26, 2007

### streeter

1. The problem statement, all variables and given/known data
A trap door, of length and width 1.55 m, is held open at an angle of 65.0° with respect to the floor. A rope is attached to the raised edge of the door and fastened to the wall behind the door in such a position that the rope pulls perpendicularly to the trap door. If the mass of the trap door is 14.6 kg, what is the torque exerted on the trap door by the rope?

2. Relevant equations
Torque=F(r)

3. The attempt at a solution

Honestly I have no clue.

2. Nov 26, 2007

### Staff: Mentor

This is a statics problem, so the sum of the moments/torques must equal zero. Find each of the moments about the pivot. One of the moments (torques) is due to the rope which is acting perpendicular to the plane (and moment arm) of the trapdoor. The other is the weight, which must be resolved into normal and parallel components with respect to the plane of the trapdoor.

Think about center of mass.