FCTC Mechanical Reasoning Principles Questions and Answers 3

Question 1

A pulley system is used to raise a 300-pound victim. If the system has a mechanical advantage of 3, how much force must the rescuer apply (ignoring friction)?

Accepted Answer

100 lbs

Answer

Force equals load divided by mechanical advantage: 300 divided by 3 equals 100 pounds.

Question 2

Which simple machine does a firefighter use when sliding a victim down a stairway on a rescue sled?

Accepted Answer

Inclined plane

Answer

An inclined plane reduces the force needed to move a load through a vertical height by spreading the work over a longer distance.

Question 3

In a compound pulley system, if you must pull 6 feet of rope to raise a load by 1 foot, what is the mechanical advantage?

Accepted Answer

6

Answer

Mechanical advantage equals effort distance divided by load distance: 6 divided by 1 equals 6.

Question 4

A fire pump impeller spins faster when driven by a larger sprocket connected by a chain to a smaller sprocket on the impeller shaft. Which sprocket is the driver?

Accepted Answer

The larger sprocket — it drives at lower RPM but speeds up the smaller driven sprocket

Answer

A large driver sprocket connected to a small driven sprocket increases the output RPM on the driven shaft, the same principle as a favorable gear ratio.

Question 5

What is the main advantage of a worm gear mechanism used in some fire apparatus equipment?

Accepted Answer

Large mechanical advantage combined with a self-locking ability

Answer

Worm gears provide high gear reduction (large mechanical advantage) and are self-locking — the worm drives the gear wheel but the gear wheel cannot back-drive the worm.

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FCTC Mechanical Reasoning Principles Questions and Answers 3