WTMA Mechanical Comprehension 4 — Questions and Answers
Question 1: An electric motor rated at 1 horsepower (HP) runs continuously. Approximately how many watts does it consume?
- 100 watts
- 350 watts
- 746 watts (Correct answer)
- 1,000 watts
Correct answer: 746 watts
One mechanical horsepower equals approximately 746 watts, a standard conversion used in motor and engine specifications.
Question 2: Which of the following best explains why a hollow steel pipe is used as a structural beam instead of a solid steel rod of equal weight?
- A hollow pipe is lighter and cheaper to ship
- A hollow pipe resists bending better due to its cross-sectional shape (Correct answer)
- A hollow pipe has less friction on its surface
- A hollow pipe is easier to weld
Correct answer: A hollow pipe resists bending better due to its cross-sectional shape
Distributing material away from the neutral axis (as in a hollow tube or I-beam) greatly increases resistance to bending with the same amount of material.
Question 3: A wheel with a 10-inch radius is connected to an axle with a 2-inch radius. If a 10-lb force is applied to the wheel rim, what force is exerted at the axle?
- 2 lbs
- 10 lbs
- 50 lbs (Correct answer)
- 100 lbs
Correct answer: 50 lbs
Mechanical advantage of a wheel and axle = wheel radius ÷ axle radius = 10/2 = 5, so output force = 10 × 5 = 50 lbs.
Question 4: A ramp (inclined plane) is 10 feet long and 2 feet high. What is its mechanical advantage?
- 0.2
- 2
- 5 (Correct answer)
- 20
Correct answer: 5
The mechanical advantage of an inclined plane = length of ramp ÷ height = 10 ÷ 2 = 5.
Question 5: A rubber bumper on a car absorbs impact energy. Which physical property makes rubber effective for this purpose?
- High thermal conductivity
- High elasticity and energy absorption (Correct answer)
- High rigidity
- Low density
Correct answer: High elasticity and energy absorption
Rubber's high elasticity allows it to deform under impact and absorb energy, then return to its original shape without transferring all force to the vehicle.
Question 6: In a series electrical circuit with three bulbs, one bulb burns out. What happens to the other two?
- They burn brighter
- They remain at the same brightness
- They also go out (Correct answer)
- They flicker continuously
Correct answer: They also go out
In a series circuit, all components share the same path; if one breaks, the circuit is open and current stops flowing through all components.
Question 7: Which tool would be most appropriate for cutting a precise circular hole in a metal sheet?
- Hacksaw
- Hole saw (Correct answer)
- Cold chisel
- File
Correct answer: Hole saw
A hole saw is a cylindrical saw bit designed to cut clean, precise circular holes in metal, wood, and other materials.
WTMA Mechanical Comprehension 4
An electric motor rated at 1 horsepower (HP) runs continuously.
Approximately how many watts does it consume?