1. The turning effect of a force about a fixed point is called:
A.
Momentum
B.
Torque
C.
Impulse
D.
Pressure
Correct Answer:
Torque
Explanation:
Torque is the turning effect produced by a force about a point or axis.
2. The SI unit of torque is:
A.
Newton
B.
Joule
C.
Newton-metre
D.
Kilogram-metre per second
Correct Answer:
Newton-metre
Explanation:
Torque is calculated as force multiplied by perpendicular distance, so its SI unit is newton-metre.
3. The magnitude of torque produced by a force F acting at a perpendicular distance r from an axis is:
A.
F + r
B.
F/r
C.
Fr
D.
r/F
Correct Answer:
Fr
Explanation:
When the force is perpendicular to the position vector, torque is given by tau = Fr.
4. A force produces maximum torque about an axis when it acts at an angle of:
A.
0 degrees to the position vector
B.
30 degrees to the position vector
C.
60 degrees to the position vector
D.
90 degrees to the position vector
Correct Answer:
90 degrees to the position vector
Explanation:
Torque is tau = rF sin theta, which is maximum when sin theta equals 1, or theta equals 90 degrees.
5. The torque of a force is zero when the line of action of the force passes through:
A.
The point of application only
B.
The axis of rotation
C.
The center of mass only
D.
The highest point of the body
Correct Answer:
The axis of rotation
Explanation:
If the line of action passes through the axis, the perpendicular distance is zero, so the torque is zero.
6. If the force applied to a body is doubled while the perpendicular distance remains unchanged, its torque becomes:
A.
Half
B.
Unchanged
C.
Double
D.
Four times
Correct Answer:
Double
Explanation:
Since torque equals force multiplied by perpendicular distance, doubling the force doubles the torque.
7. A force of 5 N acts perpendicularly at a distance of 2 m from an axis. The torque produced is:
A.
2.5 N m
B.
7 N m
C.
10 N m
D.
25 N m
Correct Answer:
10 N m
Explanation:
For a perpendicular force, torque = Fr = 5 multiplied by 2 = 10 N m.
8. The direction of torque due to a force is determined by the:
A.
Right-hand rule
B.
Law of reflection
C.
Principle of flotation
D.
Conservation of mass
Correct Answer:
Right-hand rule
Explanation:
The right-hand rule gives the direction of the torque vector from the cross product of position vector and force.
9. For the same force, which change increases the torque about an axis?
A.
Decreasing the perpendicular distance
B.
Increasing the perpendicular distance
C.
Making the distance zero
D.
Making the force act through the axis
Correct Answer:
Increasing the perpendicular distance
Explanation:
Torque is proportional to the perpendicular distance from the axis, so increasing this distance increases torque.
10. Two equal and opposite parallel forces acting along different lines form a:
A.
Single force
B.
Couple
C.
Balanced mass
D.
Radial force
Correct Answer:
Couple
Explanation:
A couple consists of two equal and opposite parallel forces whose lines of action are separated, producing a turning effect or torque.
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