OAR OAR Mechanical Comprehension: Simple Machines Questions and Answers 2 — Questions and Answers
Question 1: A worker uses a wheel and axle to lift a bucket from a well. If the wheel has a radius of 30 cm and the axle has a radius of 5 cm, what is the mechanical advantage of this system?
- 6 (Correct answer)
- 5
- 3
- 10
Correct answer: 6
The mechanical advantage of a wheel and axle equals the wheel radius divided by the axle radius: 30/5 = 6.
Question 2: Which simple machine is represented by a doorstop being pushed under a door?
- Wedge (Correct answer)
- Inclined plane
- Lever
- Screw
Correct answer: Wedge
A doorstop is a wedge, which converts force applied to its blunt end into forces perpendicular to its inclined surfaces.
Question 3: A screw has 8 threads per inch. What is the pitch of this screw?
- 1/8 inch (Correct answer)
- 8 inches
- 1/4 inch
- 1/2 inch
Correct answer: 1/8 inch
Pitch is the distance between adjacent threads, calculated as 1 divided by the number of threads per inch: 1/8 inch.
Question 4: A 200-lb crate is pushed up a 10-foot ramp to a loading dock 4 feet high. Ignoring friction, how much force is required to push the crate up the ramp?
- 80 lb (Correct answer)
- 100 lb
- 50 lb
- 200 lb
Correct answer: 80 lb
The ideal mechanical advantage of an inclined plane is length/height (10/4 = 2.5), so the required force is 200/2.5 = 80 lb.
Question 5: In a compound pulley system with 4 supporting ropes, how much effort is ideally needed to lift a 240-lb load?
- 60 lb (Correct answer)
- 80 lb
- 120 lb
- 48 lb
Correct answer: 60 lb
In an ideal compound pulley, the effort equals the load divided by the number of supporting ropes: 240/4 = 60 lb.
Question 6: A first-class lever has the fulcrum placed 2 feet from the load and 6 feet from the effort. If the load weighs 150 lb, what effort is needed to balance the lever?
- 50 lb (Correct answer)
- 75 lb
- 100 lb
- 25 lb
Correct answer: 50 lb
Using the lever principle, effort × effort arm = load × load arm, so effort = 150 × 2/6 = 50 lb.
OAR OAR Mechanical Comprehension: Simple Machines Questions and Answers 2
A worker uses a wheel and axle to lift a bucket from a well.
If the wheel has a radius of 30 cm and the axle has a radius of 5 cm, what is the mechanical advantage of this system?