Mechanical Comprehension
Mechanical Comprehension tests force, work, power, simple machines, and fluid behavior. Many items ask which arrangement gives more force or how a machine changes direction and distance.
Work, power, and machines
Work = force × distance in the direction of the force. Power = work ÷ time. Mechanical advantage (MA) = load ÷ effort. Efficiency = output work ÷ input work, so a real machine's efficiency is below 100 percent because of friction.
Levers, pulleys, and gears
Torque = force × distance from the fulcrum. A fixed pulley changes direction but has MA = 1. A movable pulley can give MA = 2, and a block and tackle multiplies force further. For meshed gears, gear ratio = teeth on driven gear ÷ teeth on driver gear; external gears turn in opposite directions.
Fluids
Pressure = force ÷ area. Fluid pressure increases with depth and depends on density and depth, not on container shape. Hydraulic systems transmit pressure undiminished, so a larger piston area produces a larger force.
Worked example
An effort of 50 N acts 2.0 m from a fulcrum and balances a load 0.50 m from the fulcrum. Using torque balance: 50 × 2.0 = L × 0.50. So 100 = 0.50L, and L = 200 N. The mechanical advantage is 200 ÷ 50 = 4. The effort moves farther than the load, which is why force is multiplied.
Traps
Use distance from the fulcrum, not total lever length. Do not confuse mechanical advantage with efficiency. A fixed pulley does not reduce force. Pressure is not the same as total force.