Torque & Equilibrium Video Lessons

Video Thumbnail

Concept

Problem: A uniform 300-N trapdoor in a ceiling is hinged at one side.a) Find the net upward force needed to begin to open it, if the upward force is applied at the center.b) Find the total force exerted on the door by the hinges, if the upward force is applied at the center.

FREE Expert Solution

Torque:

τ=rFsinθ

Newton's second law: 

ΣF=ma

Let the length of the door be L.

(a)

The weight and the applied force are at a distance L/2

The forces and radial distance are perpendicular — θ = 90°

ΣT = 0

(L/2)•mgsin 90 - (L/2)Fapplied sin 90 = 0

98% (204 ratings)
View Complete Written Solution
Problem Details

A uniform 300-N trapdoor in a ceiling is hinged at one side.

a) Find the net upward force needed to begin to open it, if the upward force is applied at the center.

b) Find the total force exerted on the door by the hinges, if the upward force is applied at the center.

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Torque & Equilibrium concept. You can view video lessons to learn Torque & Equilibrium. Or if you need more Torque & Equilibrium practice, you can also practice Torque & Equilibrium practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Lau's class at UMICH.