The more mass a substance has the more force is required to move it or to change its direction. This resistance to changes in direction is known as inertia.

The mechanical advantage (MA) of a wedge is its length divided by its thickness:

MA = \( \frac{l}{t} \) = \( \frac{9 in.}{3 in.} \) = 3

To balance this lever the torques at the green box and the blue arrow 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_a, our missing value, and plugging in our variables yields:

d_a = \( \frac{R_bd_b}{R_a} \) = \( \frac{55 lbs. \times 5 ft.}{5 lbs.} \) = \( \frac{275 ft⋅lb}{5 lbs.} \) = 55 ft.

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.

Mechanics deals with motion and the forces that produce motion.