# Homework Help: I Need Some Help Plz

1. May 6, 2008

### BrandonTex

I Need Some Help Plz !!!

Hi, I am needing some serious help on understanding the following question:

A uniform door (0.81 m wide and 2.1 m high) weighs 140 N and is hung on two hinges that fasten the long left side of the door to a vertical wall. The hinges are 2.1 m apart. Assume that the lower hinge bears all the weight of the door. Find the magnitude and direction of the horizontal component of the force applied to the door by (a ) the upper hinge and (b ) the lower hinge. Determine the magnitude and direction of the force applied by the door to (c ) the upper hinge and (d ) the lower hinge.

I have the answer in front of me from the answer book but I am having trouble understanding how they came to the final conclusion.

CAN SOMEONE EXPLAIN HOW THIS IS ANSWERED. I WILL BE FOREVER VERY GRATEFUL!!

Thank you very much!!

2. May 6, 2008

### Chi Meson

You must solve for balanced torques. Pick the lower hinge as a pivot point. The weight of the door acts as though it is a force that acts at the center of mass of the door.