FCTC FCTC Mechanical Reasoning Principles Questions and Answers 4 — Questions and Answers
Question 1: A movable pulley system lifts a 240 lb load. How much effort force is required, ignoring friction?
- 60 lbs
- 120 lbs (Correct answer)
- 180 lbs
- 240 lbs
Correct answer: 120 lbs
A single movable pulley provides a mechanical advantage of 2, so the effort needed is 240 ÷ 2 = 120 lbs.
Question 2: Two gears are connected via a belt and pulleys. The drive pulley has a 6-inch diameter and the driven pulley has a 3-inch diameter. If the drive pulley turns at 400 RPM, how fast does the driven pulley turn?
- 200 RPM
- 400 RPM
- 800 RPM (Correct answer)
- 1200 RPM
Correct answer: 800 RPM
A smaller driven pulley turns faster; speed ratio = 6 ÷ 3 = 2, so 400 × 2 = 800 RPM.
Question 3: Which type of inclined plane requires the least effort force to move a 500 lb object to a height of 4 feet?
- A ramp 8 feet long
- A ramp 10 feet long
- A ramp 16 feet long (Correct answer)
- A ramp 5 feet long
Correct answer: A ramp 16 feet long
A longer ramp provides greater mechanical advantage (MA = length ÷ height); a 16-ft ramp gives MA = 4, requiring only 125 lbs of effort.
Question 4: A wrench 12 inches long applies 30 lbs of force perpendicular to the handle. What is the torque produced on the bolt?
- 2.5 ft-lb
- 15 ft-lb
- 30 ft-lb (Correct answer)
- 360 ft-lb
Correct answer: 30 ft-lb
Torque = force × lever arm = 30 lbs × 1 ft (12 inches converted) = 30 ft-lb.
Question 5: A firefighter uses a crowbar (class 1 lever) with the fulcrum 6 inches from the load and the effort applied 48 inches from the fulcrum. What is the mechanical advantage?
- 4
- 6
- 8 (Correct answer)
- 12
Correct answer: 8
MA = effort arm ÷ load arm = 48 ÷ 6 = 8.
Question 6: A solid cylinder and a hollow cylinder of the same mass and outer radius roll down an identical incline from rest. Which reaches the bottom first?
- The hollow cylinder
- The solid cylinder (Correct answer)
- They reach the bottom at the same time
- The result depends on the incline angle
Correct answer: The solid cylinder
The solid cylinder has a lower moment of inertia, so less energy is spent on rotation and it accelerates faster down the incline.
Question 7: A pump delivers 50 gallons per minute through a 2-inch pipe. If the pipe diameter is reduced to 1 inch, what happens to the flow rate (volume per minute)?
- It increases to 200 GPM
- It remains 50 GPM (Correct answer)
- It drops to 12.5 GPM
- It drops to 25 GPM
Correct answer: It remains 50 GPM
Flow rate (volume per minute) is determined by the pump output, not the pipe diameter; only velocity changes when the pipe narrows.
FCTC FCTC Mechanical Reasoning Principles Questions and Answers 4
A movable pulley system lifts a 240 lb load.
How much effort force is required, ignoring friction?