There are two types of friction. Internal and external friction are types of friction. The coefficient of friction is independent of the force of friction.

2. Calculate the value of the coefficient of friction using the data: F=24 N, Normal force=12 N.

A. 2
B. 4
C. 8
D. 9

Answer: A

The coefficient of friction is the ratio of the friction force and normal force. It is dependent on the smoothness of the surface area.

μ=24÷12=2.

3. If the friction force value is doubled, calculate the new value of the coefficient of friction.

A. 4 times the original value
B. 2 times the original value
C. 7 times the original value
D. Remains the same

Answer: D

The value of the coefficient of friction will not change if the friction force is doubled. It only depends upon the nature of the surface.

4. The frictional force always acts in the _________ direction of motion of the body.

A. Opposite
B. Same
C. Perpendicular
D. Vertical

Answer: A

The friction of force always acts in the opposite direction of the motion of the body. It is a non-conservative force. It helps in the motion of the body.

5. Calculate the coefficient of friction if the angle of inclination is 60°.

A. 2.73
B. 1.73
C. 2.48
D. 1.41

Answer: B

The coefficient of friction is the tangent of the angle of the inclined plane. The value of μ is the tan(60°)=1.73. The coefficient of friction depends on the nature of the surface.

6. Which one of the following is the correct relationship?

A. F=μR
B. F=4μR
C. F=3μR
D. F=2μR

Answer: A

The value of the friction force is the product of the coefficient of friction and normal reaction. The correct value is F=μR.

7. Calculate the velocity of the bottom point of the wheel for perfect rolling using the data: r=20 cm, ω=100 rad/sec.

A. 20 m/sec
B. 40 m/sec
C. 60 m/sec
D. 80 m/sec

Answer: A

The velocity of the bottom point of the wheel for perfect rolling is the product of the radius and angular velocity. It is expressed in terms of m/sec.

V = r×ω = .2×100=20 m/sec.

8. The coefficient of adhesion is maximum when rails are dusty.

A. True
B. False

Answer: B

The coefficient of adhesion is maximum when rails are dry. The coefficient of adhesion depends on the nature of the material.

9. Calculate the value of the coefficient of adhesion for dusty rails if the value of the coefficient of adhesion for dry rails is .55.

A. 0.65
B. 0.89
C. 0.97
D. 0.48

Answer: D

The value of the coefficient of adhesion for dusty rails is .48. The value of the coefficient of adhesion for dry rails is maximum.

10. Calculate the value measured by Moving Iron when a sinusoidal voltage signal V(t) = √2sin(3ωt) is applied to it.

A. 2 V
B. 1 V
C. 3 V
D. 4 V

Answer: B

Moving iron instrument measures the r.m.s value of the input signal. The r.m.s value of the sinusoidal signal is