OAR OAR Mechanical Comprehension: Forces 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 force acting on the box?
- 30 N in the direction of the push (Correct answer)
- 70 N in the direction of the push
- 20 N opposite the push
- 50 N in the direction of the push
Correct answer: 30 N in the direction of the push
Net force equals applied force minus friction: 50 N − 20 N = 30 N in the direction of the push.
Question 2: Two forces act on an object: 8 N to the east and 6 N to the north. What is the magnitude of the resultant force?
- 10 N (Correct answer)
- 14 N
- 2 N
- 7 N
Correct answer: 10 N
Using the Pythagorean theorem, the resultant is √(8² + 6²) = √(64 + 36) = √100 = 10 N.
Question 3: A 5 kg object hangs motionless from a rope attached to the ceiling. What is the tension in the rope? (g = 9.8 m/s²)
- 49 N (Correct answer)
- 5 N
- 25 N
- 98 N
Correct answer: 49 N
The tension equals the weight of the object: T = mg = 5 × 9.8 = 49 N.
Question 4: According to Newton's Third Law, when a hammer strikes a nail, how does the force the nail exerts on the hammer compare to the force the hammer exerts on the nail?
- Equal in magnitude but opposite in direction (Correct answer)
- Less because the nail is smaller
- Greater because the nail decelerates the hammer
- Zero because the nail moves
Correct answer: Equal in magnitude but opposite in direction
Newton's Third Law states that action and reaction forces are always equal in magnitude and opposite in direction.
Question 5: A spring with a spring constant of 200 N/m is compressed 0.15 m from its natural length. What force does the spring exert?
- 30 N (Correct answer)
- 15 N
- 300 N
- 20 N
Correct answer: 30 N
By Hooke's Law, F = kx = 200 × 0.15 = 30 N.
Question 6: An object weighing 80 N sits on a ramp inclined at 30° above the horizontal. What is the component of the gravitational force acting parallel to the ramp surface?
- 40 N (Correct answer)
- 69.3 N
- 80 N
- 56.6 N
Correct answer: 40 N
The parallel component equals W × sin(30°) = 80 × 0.5 = 40 N.
OAR OAR Mechanical Comprehension: Forces 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 force acting on the box?