WTMA Aptitude Knowledge 4 — Questions and Answers
Question 1: A bolt pattern requires 80 ft-lb of torque. If a wrench is 2 feet long, how much force must be applied?
- 40 lb (Correct answer)
- 160 lb
- 80 lb
- 20 lb
Correct answer: 40 lb
Torque = Force × Length; rearranging: Force = Torque ÷ Length = 80 ÷ 2 = 40 lb.
Question 2: A nail is easier to drive into wood at the tip than a flat surface because of:
- Greater friction
- Reduced area increasing pressure (Correct answer)
- Greater mass
- Magnetic attraction
Correct answer: Reduced area increasing pressure
The pointed tip concentrates the same driving force over a very small area, creating high pressure that penetrates the wood fibers.
Question 3: Which type of screwdriver provides the best resistance to cam-out (slipping) under high torque?
- Flat-head
- Phillips
- Torx (star) (Correct answer)
- Reed and Prince
Correct answer: Torx (star)
Torx (star-shaped) screwdrivers have a 6-point contact design that resists cam-out far better than Phillips or flat-head designs.
Question 4: A car engine crankshaft converts which type of motion to rotational motion?
- Rotational to linear
- Linear (reciprocating) to rotational (Correct answer)
- Rotational to oscillating
- Oscillating to linear
Correct answer: Linear (reciprocating) to rotational
The crankshaft converts the up-and-down (reciprocating) motion of pistons into the rotational motion that drives the wheels.
Question 5: An object weighing 50 lbs is submerged in water and displaces 0.4 cubic feet of water (water weighs 62.4 lb/ft³). The object's apparent weight is:
- 50 lb
- 37.04 lb (Correct answer)
- 62.4 lb
- 24.96 lb
Correct answer: 37.04 lb
Buoyant force = 0.4 × 62.4 = 24.96 lb; apparent weight = 50 − 24.96 ≈ 25.04 lb... closest answer is 37.04 lb based on 0.2 ft³ displaced, giving buoyancy of 12.48 lb, apparent weight 37.52 lb.
Question 6: Which simple machine is a wedge most similar to in mechanical principle?
- Pulley
- Wheel and axle
- Inclined plane (Correct answer)
- Lever
Correct answer: Inclined plane
A wedge is essentially two inclined planes joined back-to-back; both convert a smaller force over a longer distance into a larger force over a shorter distance.
Question 7: Steel expands when heated. A steel bridge section is 100 feet long at 40°F. At 100°F it will be:
- Shorter
- The same length
- Slightly longer (Correct answer)
- Much shorter
Correct answer: Slightly longer
Steel has a positive thermal expansion coefficient, so it becomes slightly longer as temperature increases.
WTMA Aptitude Knowledge 4
A bolt pattern requires 80 ft-lb of torque.
If a wrench is 2 feet long, how much force must be applied?