Test Pulleys, Gears, and Levers Questions and Answers Flashcards

A firefighter uses a Halligan bar as a lever to force open a door. Moving the fulcrum closer to the load will:

Answer: Increase the mechanical advantage

Moving the fulcrum closer to the load lengthens the effort arm relative to the load arm, increasing mechanical advantage.

Two gears mesh together: the driver has 20 teeth spinning at 100 RPM and the driven gear has 50 teeth. What is the speed of the driven gear?

Answer: 40 RPM

Speed ratio = teeth of driver ÷ teeth of driven = 20/50, so driven gear speed = 100 × (20/50) = 40 RPM.

A rope rescue team rigs a 2:1 pulley system. If they pull 10 feet of rope, how high does the victim rise?

Answer: 5 feet

With a 2:1 system the load rises half the distance the rope is pulled: 10 ÷ 2 = 5 feet.

Which class of lever always has a mechanical advantage less than 1?

Answer: Third class

Third-class levers always have the effort between the fulcrum and the load, resulting in a mechanical advantage less than 1 but greater speed and range.

Two gears of equal size are meshed together. A drives B at 200 RPM. What speed does Gear B rotate at?

Answer: 200 RPM

Gears with equal numbers of teeth have a 1:1 ratio, so Gear B rotates at the same 200 RPM as Gear A.

A pulley is described as having 'friction losses.' This means that in practice the actual mechanical advantage will be:

Answer: Lower than the theoretical value

Friction in pulleys and ropes consumes some of the input force, so actual (practical) mechanical advantage is always less than the ideal theoretical value.

A second-class lever has an effort arm of 8 feet and a load arm of 2 feet. The load is 300 lbs. How much effort is needed?

Answer: 75 lbs

Effort = Load × (Load arm ÷ Effort arm) = 300 × (2 ÷ 8) = 75 lbs.