Astudent sets a board to pivot about its center. the student then places a box with mass m at some position r from the pivot point. the student plans to place a second box with mass 2 m on the other side of the board. in terms of r, where should the box be placed in order to maintain static equilibrium?

The box should be placed at a distance of from the pivot

Explanation:

In order to be in static equilibrium, both Torques have to be the same magnitude, so:

  Replacing the formula for Torque:

  where X is the distance we need to find.

Solving for X we get:

As we can see, the distance does not depend on the actual value of the mass but on the fact of one being twice as much as the other one.

b. lifting dumbbell weight at 20-degree angle from the body after a 45-degree angle