FCTC Test Pulleys, Gears, and Levers Questions and Answers 2 — Questions and Answers
Question 1: A fixed pulley is used to redirect a rope. A firefighter pulls down with 100 lbs of force. How much weight can be lifted?
- 50 lbs
- 100 lbs (Correct answer)
- 200 lbs
- 400 lbs
Correct answer: 100 lbs
A single fixed pulley only changes the direction of force and provides no mechanical advantage, so output force equals input force.
A fixed pulley's only function is changing the direction of force, such as pulling down to lift upward. Mechanical advantage equals 1, so 100 lbs of pull lifts exactly 100 lbs. To gain mechanical advantage, movable pulleys must be added to create a compound pulley system.
Question 2: A two-gear set has a driver gear with 30 teeth and a driven gear with 60 teeth. If the driver gear turns at 200 RPM, at what RPM does the driven gear turn?
- 100 RPM (Correct answer)
- 200 RPM
- 400 RPM
- 600 RPM
Correct answer: 100 RPM
Speed ratio equals driver teeth divided by driven teeth: 30 divided by 60 equals 0.5; driven gear RPM equals 200 times 0.5 equals 100 RPM.
Gear ratio: driven RPM equals driver RPM times (driver teeth divided by driven teeth). 200 times (30 divided by 60) equals 100 RPM. The driven gear has twice the teeth of the driver so it rotates at half the speed. This trades rotational speed for increased torque, common in heavy machinery drives.
Question 3: A Class 2 lever has the load between the fulcrum and the effort. If the load is 150 lbs and the mechanical advantage is 3, how much effort is required?
- 30 lbs
- 50 lbs (Correct answer)
- 75 lbs
- 150 lbs
Correct answer: 50 lbs
Effort equals load divided by mechanical advantage: 150 divided by 3 equals 50 lbs.
In a Class 2 lever (wheelbarrow is a common example) the load is between the fulcrum and the effort. With MA of 3, effort equals 150 divided by 3 equals 50 lbs. Class 2 levers always provide mechanical advantage greater than 1, making them ideal for moving heavy loads with reduced effort.
Question 4: Three equal weights hang from a balanced beam. Two hang 2 feet from the fulcrum on the left side and one hangs on the right side. How far from the fulcrum must the single weight hang to balance the beam?
- 1 foot
- 2 feet
- 4 feet (Correct answer)
- 6 feet
Correct answer: 4 feet
Torque balance: 2W times 2 ft equals 4Wft on the left. To balance: 1W times d equals 4Wft, so d equals 4 feet.
Torque (moment) must balance on both sides: left side equals 2 times W times 2 ft equals 4Wft; right side equals 1 times W times d. Setting equal: 4Wft equals Wd, so d equals 4 feet. Moment calculations are used in aerial ladder operations to ensure loads do not exceed rated capacity at given extension lengths.
Question 5: A compound gear train has a first stage ratio of 4:1 and a second stage ratio of 3:1. What is the total gear reduction?
- 7:1
- 12:1 (Correct answer)
- 16:1
- 24:1
Correct answer: 12:1
Total ratio equals first stage times second stage: 4 times 3 equals 12:1.
Compound gear trains multiply individual stage ratios: 4:1 times 3:1 equals 12:1. This means the output shaft rotates at one-twelfth the speed of the input but with 12 times the torque. Hydraulic pump drives on fire apparatus use compound gear trains to achieve the required pump shaft speed.
Question 6: A fulcrum is placed at the exact midpoint of a lever. A 200-lb load is on one end. What force is needed at the other end to lift the load?
- 50 lbs
- 100 lbs
- 200 lbs (Correct answer)
- 400 lbs
Correct answer: 200 lbs
With the fulcrum at the midpoint, the effort arm equals the load arm, so MA equals 1 and effort equals load equals 200 lbs.
MA equals effort arm divided by load arm. When both arms are equal with the fulcrum at the midpoint, MA equals 1 and effort equals load. This is why firefighters grip forcible entry tools as far from the contact point as possible — maximizing the effort arm increases mechanical advantage.
FCTC Test Pulleys, Gears, and Levers Questions and Answers 2
A fixed pulley is used to redirect a rope.
A firefighter pulls down with 100 lbs of force.
How much weight can be lifted?