Question

You're in the middle of moving and need to bring furniture and into your new house. You want to prop the door open, but your dog ate the doorstopper (and your homework). All you can find is a large brick. If you want to impart the largest torque on the door to keep it open, where should you place the brick?

A) Put the brick as close to the hinges as possible.
B) Put the brick in the middle of the door.
C) Put the brick as far from the hinges as possible.

Answer 1

C) Put the brick as far from the hinges as possible

Step-by-step explanation:

As torque is the product of the force around the rotation point and the distance to the pivot point, and the mass (force) of the brick stays constant, what we can do to maximize the torque is maximize the distance to the pivot point, aka the hinge. So we should put the brick as far from the hinges as possible.