Mechanical Aptitude Mechanical Aptitude Forces and Motion Principles 3 — Questions and Answers
Question 1: A wrench applies a force of 30 N at a distance of 0.2 m from a bolt. What is the torque produced?
- 0.6 N·m
- 6 N·m (Correct answer)
- 60 N·m
- 150 N·m
Correct answer: 6 N·m
Torque = force × distance = 30 N × 0.2 m = 6 N·m.
Question 2: Which type of friction acts on an object that is sliding across a surface?
- Static friction
- Kinetic friction (Correct answer)
- Rolling friction
- Fluid friction
Correct answer: Kinetic friction
Kinetic (sliding) friction acts between surfaces in relative motion against each other.
Question 3: An object moving in a circle at constant speed is subject to a net force directed:
- Outward from the center
- Tangent to the circle
- Toward the center (Correct answer)
- Upward against gravity
Correct answer: Toward the center
Centripetal force always points toward the center of the circular path.
Question 4: A 2 kg object moving at 4 m/s has a kinetic energy of:
- 4 J
- 8 J
- 16 J (Correct answer)
- 32 J
Correct answer: 16 J
KE = ½mv² = ½ × 2 × 4² = ½ × 2 × 16 = 16 J.
Question 5: Which of the following correctly states Newton's third law?
- An object at rest stays at rest unless acted upon by a force
- Force equals mass times acceleration
- For every action there is an equal and opposite reaction (Correct answer)
- The net force equals the rate of change of momentum
Correct answer: For every action there is an equal and opposite reaction
Newton's third law states that action-reaction pairs are always equal in magnitude and opposite in direction.
Question 6: If you push a heavy crate with 100 N and it doesn't move, what does that tell you about static friction?
- Static friction is less than 100 N
- Static friction equals exactly 100 N (Correct answer)
- Static friction is greater than 100 N
- Static friction is zero
Correct answer: Static friction equals exactly 100 N
Since the crate is in equilibrium (not moving), static friction must equal the applied force of 100 N.
Question 7: A sled slides down a hill and gains speed. Which force is primarily responsible for this acceleration?
- Normal force
- Static friction
- The component of gravity parallel to the slope (Correct answer)
- Air resistance
Correct answer: The component of gravity parallel to the slope
The component of gravity acting along the slope (parallel component) pulls the sled downhill, causing it to accelerate.
Mechanical Aptitude Mechanical Aptitude Forces and Motion Principles 3
A wrench applies a force of 30 N at a distance of 0.2 m from a bolt.
What is the torque produced?