OAR OAR Mechanical Comprehension: Forces 4 ā Questions and Answers
Question 1: A lever has its fulcrum at the center. A 40 N force is applied 2 m from the fulcrum. To balance, what force must be applied 4 m from the fulcrum on the other side?
- 80 N
- 20 N (Correct answer)
- 40 N
- 10 N
Correct answer: 20 N
Torque balance: 40 Ć 2 = F Ć 4 ā F = 80/4 = 20 N.
Question 2: Which quantity represents the rotational effect of a force about a pivot point?
- Momentum
- Torque (Correct answer)
- Impulse
- Power
Correct answer: Torque
Torque (Ļ = F Ć d) measures a force's tendency to cause rotation about a pivot.
Question 3: An object moves in a circle at constant speed. The net force on the object is directed:
- Tangent to the circle
- Outward from the center
- Inward toward the center (Correct answer)
- Opposite to velocity
Correct answer: Inward toward the center
Centripetal force always points toward the center of the circle to maintain circular motion.
Question 4: Two workers push a crate in the same direction: one with 250 N and one with 180 N. A friction force of 130 N opposes motion. What is the net force?
- 560 N
- 300 N (Correct answer)
- 430 N
- 60 N
Correct answer: 300 N
Net force = (250 + 180) ā 130 = 430 ā 130 = 300 N in the direction of motion.
Question 5: If you double the mass of an object while keeping the net force constant, what happens to its acceleration?
- Doubles
- Stays the same
- Quadruples
- Halves (Correct answer)
Correct answer: Halves
From a = F/m, doubling m while holding F constant cuts acceleration in half.
Question 6: A spring scale reads 80 N when a block hangs at rest. The block is then placed on a frictionless table and pulled horizontally with 80 N. What is the normal force from the table?
- 0 N
- 160 N
- 80 N (Correct answer)
- 113 N
Correct answer: 80 N
The normal force balances gravity (weight = 80 N); the horizontal pull does not affect the vertical normal force.
Question 7: A 1,000 N crate is dragged up a frictionless ramp inclined at 30Ā°. What force parallel to the ramp is needed to move it at constant speed?
- 500 N (Correct answer)
- 866 N
- 1,000 N
- 1,154 N
Correct answer: 500 N
Force needed = mg sin 30Ā° = 1,000 Ć 0.5 = 500 N (frictionless, constant speed = equilibrium).
OAR OAR Mechanical Comprehension: Forces 4
A lever has its fulcrum at the center.
A 40 N force is applied 2 m from the fulcrum.
To balance, what force must be applied 4 m from the fulcrum on the other side?