FCTC Mechanical Reasoning Principles Questions and Answers Flashcards

A movable pulley system lifts a 240 lb load. How much effort force is required, ignoring friction?

Answer: 120 lbs

A single movable pulley provides a mechanical advantage of 2, so the effort needed is 240 ÷ 2 = 120 lbs.

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?

Answer: 800 RPM

A smaller driven pulley turns faster; speed ratio = 6 ÷ 3 = 2, so 400 × 2 = 800 RPM.

Which type of inclined plane requires the least effort force to move a 500 lb object to a height of 4 feet?

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.

A wrench 12 inches long applies 30 lbs of force perpendicular to the handle. What is the torque produced on the bolt?

Answer: 30 ft-lb

Torque = force × lever arm = 30 lbs × 1 ft (12 inches converted) = 30 ft-lb.

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?

Answer: 8

MA = effort arm ÷ load arm = 48 ÷ 6 = 8.

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?

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.

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)?

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.