IBEW Mechanical Reasoning Principles 3 — Questions and Answers
Question 1: A hydraulic jack has a small piston with a 1 sq-in area and a large piston with a 20 sq-in area. A 50 lb force on the small piston generates how much force on the large piston?
- 2.5 lb
- 70 lb
- 1000 lb (Correct answer)
- 500 lb
Correct answer: 1000 lb
Pascal's principle: force output = force input × (area output / area input) = 50 × 20 = 1000 lb.
Question 2: A shaft transmits power through a V-belt to a driven pulley. If the driver pulley has a 4-inch diameter and spins at 1800 RPM, what is the RPM of a 12-inch driven pulley?
- 5400 RPM
- 600 RPM (Correct answer)
- 450 RPM
- 900 RPM
Correct answer: 600 RPM
Speed ratio = 4/12 = 1/3; driven RPM = 1800 × (1/3) = 600 RPM.
Question 3: A cam converts which type of motion to another?
- Rotary motion to linear (reciprocating) motion (Correct answer)
- Linear motion to rotary motion
- Oscillating motion to hydraulic pressure
- Electrical energy to mechanical energy
Correct answer: Rotary motion to linear (reciprocating) motion
A cam is a rotating or sliding piece that converts rotary motion into a follower's reciprocating or oscillating linear motion.
Question 4: Which class of lever has the effort between the fulcrum and the load?
- Class 1
- Class 2
- Class 3 (Correct answer)
- Class 4
Correct answer: Class 3
In a Class 3 lever the effort is applied between the fulcrum and the load, as seen in a pair of tweezers.
Question 5: A ratchet and pawl mechanism is used primarily to:
- Increase speed of rotation
- Multiply torque continuously
- Allow rotation in one direction only (Correct answer)
- Convert rotary to linear motion
Correct answer: Allow rotation in one direction only
The pawl engages the ratchet teeth to permit rotation in one direction while preventing reverse rotation.
Question 6: Two objects of identical size are dropped from the same height — one is solid steel, the other solid aluminum. Ignoring air resistance, which hits the ground first?
- The steel object, because it is heavier
- The aluminum object, because it is lighter
- They hit at the same time (Correct answer)
- Whichever has the smoother surface
Correct answer: They hit at the same time
In the absence of air resistance, all objects fall with the same gravitational acceleration regardless of mass.
Question 7: A pipe carrying compressed air develops a small crack. The air leaks outward rather than the outside air leaking in because of:
- Gravity acting on the air molecules
- Higher pressure inside the pipe (Correct answer)
- The crack's shape directing flow
- Bernoulli's principle
Correct answer: Higher pressure inside the pipe
Fluids flow from regions of higher pressure to lower pressure; the compressed air inside has higher pressure than the atmosphere outside.
IBEW Mechanical Reasoning Principles 3
A hydraulic jack has a small piston with a 1 sq-in area and a large piston with a 20 sq-in area.
A 50 lb force on the small piston generates how much force on the large piston?