To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

Solving for d_b, our missing value, and plugging in our variables yields:

d_b = \( \frac{R_ad_a}{R_b} \) = \( \frac{5 lbs. \times 5 ft.}{20 lbs.} \) = \( \frac{25 ft⋅lb}{20 lbs.} \) = 1.25 ft.

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{560 lbs.}{70 lbs.} \) = 8

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.

Mechanics deals with motion and the forces that produce motion.

The Joule (J) is the standard unit of energy and has the unit \({kg \times m^2} \over s^2\).