Mechanical Aptitude Test Mechanical Aptitude Forces and Motion Principles 1 — Questions and Answers
Question 1: A 5 kg cart is pulled by a rope exerting 30 N of force. Friction opposes the motion with 5 N. What is the acceleration of the cart?
- 5 m/s² (Correct answer)
- 6 m/s²
- 4 m/s²
- 7 m/s²
Correct answer: 5 m/s²
Net force = 30 N − 5 N = 25 N. Using Newton's second law, a = F/m = 25 N ÷ 5 kg = 5 m/s².
Question 2: A 1,200 kg car decelerates from 20 m/s to a complete stop in 4 seconds. What average braking force was applied?
- 3,000 N
- 4,800 N
- 6,000 N (Correct answer)
- 9,600 N
Correct answer: 6,000 N
Deceleration = Δv / t = 20 / 4 = 5 m/s². Braking force = m × a = 1,200 × 5 = 6,000 N.
Question 3: A 2 kg ball is dropped from rest and falls freely for 3 seconds (g = 10 m/s²). What is its velocity just before it hits the ground?
- 10 m/s
- 20 m/s
- 30 m/s (Correct answer)
- 60 m/s
Correct answer: 30 m/s
Using v = u + at with u = 0, v = 0 + (10)(3) = 30 m/s. Gravity accelerates the ball by 10 m/s every second.
Question 4: Three forces act on a single object: 40 N east, 40 N west, and 20 N north. What is the net resultant force?
- 0 N
- 20 N north (Correct answer)
- 80 N east
- 100 N northeast
Correct answer: 20 N north
The 40 N east and 40 N west forces cancel each other out, leaving only the 20 N northward force as the net resultant.
Question 5: A stationary 8 kg block has a constant 24 N force applied to it. How far does it travel in 3 seconds?
- 9 m
- 13.5 m (Correct answer)
- 27 m
- 36 m
Correct answer: 13.5 m
Acceleration a = F/m = 24/8 = 3 m/s². Distance d = ½at² = ½ × 3 × 9 = 13.5 m.
Question 6: A rocket in space fires its engine, expelling exhaust gases backward. According to Newton's third law, what happens to the rocket?
- It remains stationary because there is nothing to push against in space
- It accelerates forward with a force equal in magnitude to the exhaust thrust (Correct answer)
- It decelerates because it loses mass as fuel is expelled
- It moves sideways due to the rotation of expelled gases
Correct answer: It accelerates forward with a force equal in magnitude to the exhaust thrust
Newton's third law states every action has an equal and opposite reaction. The rocket pushes gases backward, so the gases push the rocket forward with equal force — no external surface is needed.
Mechanical Aptitude Test Mechanical Aptitude Forces and Motion Principles 1
A 5 kg cart is pulled by a rope exerting 30 N of force.
Friction opposes the motion with 5 N.
What is the acceleration of the cart?