BARB Mechanical Comprehension 2 — Questions and Answers
Question 1: A wheel has a radius of 0.5 m and rotates at 2 revolutions per second. What is the linear speed of a point on its rim?
- π m/s
- 4π m/s
- 2π m/s (Correct answer)
- 3π m/s
Correct answer: 2π m/s
Circumference = 2π × 0.5 = π m; Linear speed = π × 2 = 2π m/s.
Question 2: A hydraulic jack has an input piston area of 5 cm² and an output piston area of 50 cm². A 10 N force on the input produces what output force?
- 10 N
- 50 N
- 200 N
- 100 N (Correct answer)
Correct answer: 100 N
Mechanical advantage = 50 ÷ 5 = 10; Output force = 10 × 10 = 100 N.
Question 3: Two objects are connected by a rope over a frictionless pulley. Object A weighs 8 kg and Object B weighs 5 kg. Which way will the system move?
- Object B descends
- They remain stationary
- Object A descends (Correct answer)
- They oscillate indefinitely
Correct answer: Object A descends
Object A is heavier (8 kg > 5 kg), so it will descend and Object B will rise.
Question 4: A spring stretches 5 cm when a 10 N force is applied. What force is needed to stretch it 15 cm?
- 20 N
- 35 N
- 25 N
- 30 N (Correct answer)
Correct answer: 30 N
Spring constant k = 10 ÷ 0.05 = 200 N/m; Force = 200 × 0.15 = 30 N.
Question 5: Gear A (10 teeth) drives Gear B (30 teeth) which is on the same shaft as Gear C (10 teeth). Gear C drives Gear D (20 teeth). If Gear A turns at 300 rpm, what is Gear D's speed?
- 100 rpm
- 75 rpm
- 50 rpm (Correct answer)
- 150 rpm
Correct answer: 50 rpm
A→B: 300 × (10/30) = 100 rpm; B and C share a shaft so C = 100 rpm; C→D: 100 × (10/20) = 50 rpm.
Question 6: Which simple machine is a wedge most similar to in terms of mechanical principle?
- Pulley
- Wheel and axle
- Inclined plane (Correct answer)
- Lever
Correct answer: Inclined plane
A wedge is essentially a moving inclined plane that converts force direction to split or lift objects.
BARB Mechanical Comprehension 2
A wheel has a radius of 0.5 m and rotates at 2 revolutions per second.
What is the linear speed of a point on its rim?