# Torque and Door Hinges

I'm having quite a bit of trouble with this problem. It seems easy, but I just can't seem to get the idea.

The Problem said:
A door has a height of 2.1m along a y axis that extends vertically upward and a width of 0.91 m along an x axis that extends outward from the hinged edge of the door. A hinge 0.30 m from the top and a hinge 0.30 m from the bootom each support half the door's mass, which is 27kg. In unit-vector notation, what are the forces on the door at a) the top hinge and b) the bottom hinge.

I'm able to calculate the vertical components of the forces by using the summation of forces in the y direction equal to zero. The horizantal components, i'm pretty sure I need to use summation of torques, but there are only two forces! The force from each hinge in the horizantal direction! How would I go about solving htis?

## Answers and Replies

Doc Al
Mentor
You are given the vertical components of the force the hinges exert on the door. To find the horizontal components, take each hinge as a pivot point and realize that the torques about that point must add to zero.