WTMA Mechanical Comprehension 5 — Questions and Answers
Question 1: A centrifugal pump spins faster. What happens to the water pressure it produces?
- Pressure decreases
- Pressure stays the same
- Pressure increases (Correct answer)
- Pressure fluctuates randomly
Correct answer: Pressure increases
Centrifugal pumps use rotational speed to impart kinetic energy to fluid; higher speed increases the centrifugal force and therefore the output pressure.
Question 2: A conveyor belt is driven by a large pulley (diameter 20 in) connected by a belt to a small pulley (diameter 5 in) on a motor. If the motor spins at 400 RPM, how fast does the large pulley turn?
- 25 RPM
- 100 RPM (Correct answer)
- 400 RPM
- 1,600 RPM
Correct answer: 100 RPM
Speed ratio inversely follows the diameter ratio: large pulley speed = 400 × (5/20) = 100 RPM.
Question 3: Which statement best describes the purpose of a torque wrench?
- It removes bolts faster than a standard wrench
- It applies a precisely measured rotational force to a fastener (Correct answer)
- It grips rounded bolt heads better
- It extends reach into tight spaces
Correct answer: It applies a precisely measured rotational force to a fastener
A torque wrench measures and limits the rotational force applied to a fastener, preventing over-tightening that can strip threads or break bolts.
Question 4: Two objects with different masses are dropped from the same height in a vacuum. Which hits the ground first?
- The heavier object
- The lighter object
- They hit at the same time (Correct answer)
- It depends on their shape
Correct answer: They hit at the same time
In a vacuum, gravity accelerates all objects equally regardless of mass (9.8 m/s²), so both objects fall at identical rates and land simultaneously.
Question 5: A screwdriver is turned 10 full rotations to drive a screw 0.5 inches into wood. What is the thread pitch of the screw?
- 0.025 inches per turn
- 0.05 inches per turn (Correct answer)
- 0.5 inches per turn
- 5 inches per turn
Correct answer: 0.05 inches per turn
Thread pitch = total distance ÷ number of turns = 0.5 ÷ 10 = 0.05 inches per turn.
Question 6: A steel beam expands when heated. This property is known as:
- Thermal conductivity
- Thermal expansion (Correct answer)
- Heat capacity
- Thermal resistance
Correct answer: Thermal expansion
Thermal expansion is the tendency of matter to change its dimensions in response to a change in temperature, critical in bridge and rail design.
Question 7: Which type of gear arrangement is used to change the direction of rotation by 90 degrees?
- Spur gears
- Helical gears
- Bevel gears (Correct answer)
- Rack and pinion
Correct answer: Bevel gears
Bevel gears have angled teeth cut on a conical surface, allowing them to transmit motion and power between shafts at right angles (90°) to each other.
WTMA Mechanical Comprehension 5
A centrifugal pump spins faster.
What happens to the water pressure it produces?