Mechanical Aptitude Mechanical Aptitude Forces and Motion Principles Questions and Answers 2 — Questions and Answers
Question 1: A 10 kg box is pushed across a floor with a force of 50 N while friction exerts 20 N in the opposite direction. What is the net acceleration of the box?
- 3 m/s² (Correct answer)
- 5 m/s²
- 2 m/s²
- 7 m/s²
Correct answer: 3 m/s²
Net force is 50 N - 20 N = 30 N, and acceleration = 30 N / 10 kg = 3 m/s².
Question 2: An object is moving at a constant velocity along a straight path. What can you conclude about the forces acting on it?
- The net force is zero (Correct answer)
- There is no friction
- Only gravity acts on it
- The applied force is increasing
Correct answer: The net force is zero
Constant velocity means zero acceleration, which by Newton's first law means the net force is zero.
Question 3: A baseball pitcher throws a 0.15 kg ball at 40 m/s. If the throw takes 0.5 seconds, what average force did the pitcher apply?
- 12 N (Correct answer)
- 6 N
- 20 N
- 15 N
Correct answer: 12 N
Force = mass × change in velocity / time = 0.15 kg × 40 m/s / 0.5 s = 12 N.
Question 4: Two ropes are attached to a heavy crate. Rope A pulls north with 100 N and Rope B pulls east with 100 N. What is the approximate magnitude of the resultant force?
- 141 N (Correct answer)
- 200 N
- 100 N
- 50 N
Correct answer: 141 N
The resultant of two perpendicular 100 N forces is √(100² + 100²) ≈ 141 N.
Question 5: A 5 kg object falls freely from rest near Earth's surface. Ignoring air resistance, what is its speed after 3 seconds?
- 29.4 m/s (Correct answer)
- 15 m/s
- 45 m/s
- 9.8 m/s
Correct answer: 29.4 m/s
Speed = g × t = 9.8 m/s² × 3 s = 29.4 m/s.
Question 6: A worker pushes a 40 kg cart up a frictionless ramp inclined at 30°. What minimum force parallel to the ramp is needed to keep the cart from sliding down?
- 196 N (Correct answer)
- 392 N
- 340 N
- 98 N
Correct answer: 196 N
The component of gravity along the ramp is mg sin(30°) = 40 × 9.8 × 0.5 = 196 N.
Mechanical Aptitude Mechanical Aptitude Forces and Motion Principles Questions and Answers 2
A 10 kg box is pushed across a floor with a force of 50 N while friction exerts 20 N in the opposite direction.
What is the net acceleration of the box?