FREE CPS Firefighter Test Mechanical Aptitude Principles Questions and Answers Flashcards

A firefighter uses a block-and-tackle system with 4 rope segments supporting the load. To lift a 400 lb victim from a confined space, the minimum effort force required (ignoring friction) is:

Answer: 100 lb

The mechanical advantage of a block-and-tackle equals the number of rope segments supporting the load, so effort = 400 ÷ 4 = 100 lb.

A wrench with a 12-inch handle requires 30 ft-lb of torque to loosen a bolt. If a firefighter switches to an 18-inch handle wrench, the force needed to achieve the same torque is:

Answer: 20 lb

Torque = Force × Length, so Force = Torque ÷ Length = 360 in-lb ÷ 18 in = 20 lb.

A fire engine pump produces pressure of 150 psi. The hose has a cross-sectional area of 3 in². What is the force exerted by the water on a closed nozzle cap?

Answer: 450 lb

Force = Pressure × Area = 150 psi × 3 in² = 450 lb.

When a firefighter compresses air into a SCBA cylinder, the temperature of the air inside rises. This best illustrates:

Answer: Gay-Lussac's Law — pressure and temperature increase together

Gay-Lussac's Law states that at constant volume, gas pressure and absolute temperature are directly proportional; compressing air raises both pressure and temperature.

A firefighter pushes a 300 lb cabinet up a 15-foot ramp that rises 3 feet vertically. Ignoring friction, the mechanical advantage of the ramp is:

Answer: 5

The mechanical advantage of an inclined plane equals the ramp length divided by the rise: 15 ÷ 3 = 5.

Two identical fire hoses carry water at the same velocity. Hose A is coiled flat with no kinks; Hose B has a sharp 90-degree kink. Compared to Hose A, Hose B will have:

Answer: Lower flow rate due to increased resistance at the kink

A kink sharply increases flow resistance, reducing the effective cross-sectional area and causing a significant drop in flow rate.