Friction — MH-CET Physics MCQs with Solutions
Free MH-CET Physics Friction MCQs with step-by-step solutions (21 questions). Part of Laws of Motion (Std 11). Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Friction · easy · theory
Static friction is the frictional force that acts:
A. Only on rolling bodies
B. Between surfaces in relative motion
C. Only in the absence of an applied force
D. Between surfaces at rest relative to each other ✓ Correct
Solution: It adjusts itself up to a maximum value called limiting friction.
Q2 — Friction · medium · theory
The coefficients of static and kinetic friction are related by:
A. $\mu_s < \mu_k$
B. $\mu_s = \mu_k$
C. They are unrelated
D. $\mu_s > \mu_k$ ✓ Correct
Solution: This is why a heavy box is harder to start moving than to keep moving.
Q3 — Friction · easy · theory
Friction always acts in a direction that:
A. Is perpendicular to the surfaces
B. Assists the applied force
C. Is vertically downward
D. Opposes the relative motion or the tendency to relative motion ✓ Correct
Solution: It is a self-adjusting force in the static case.
Q4 — Friction · medium · theory
The force of limiting friction between two surfaces is:
A. Independent of the apparent area of contact ✓ Correct
B. Inversely proportional to the normal reaction
C. Proportional to the area of contact
D. Independent of the normal reaction
Solution: It depends only on the nature of the surfaces and the normal reaction.
Q5 — Friction · hard · theory
The angle of friction is the angle between the:
A. Resultant of the normal reaction and limiting friction, and the normal reaction ✓ Correct
B. Normal reaction and the vertical
C. Applied force and the surface
D. Two surfaces in contact
Solution: Its tangent equals the coefficient of static friction.
Q6 — Friction · medium · theory
The angle of repose is the angle of an inclined plane at which a body:
A. Leaves the surface
B. Just begins to slide down of its own accord ✓ Correct
C. Moves with uniform acceleration
D. Remains permanently at rest
Solution: At this angle $\tan\theta = \mu_s$, so it equals the angle of friction.
Q7 — Friction · easy · theory
Of sliding, static and rolling friction, the smallest for given surfaces is:
A. Static friction
B. They are all equal
C. Sliding friction
D. Rolling friction ✓ Correct
Solution: This is why wheels and ball bearings are used to reduce resistance to motion.
Q8 — Friction · medium · theory
Friction is sometimes described as a necessary evil because it:
A. Only ever helps motion
B. Only ever wastes energy
C. Wastes energy yet makes walking and braking possible ✓ Correct
D. Has no effect on machines
Solution: Without it a person could not walk and a vehicle could not be steered or stopped.
Q9 — Friction · medium · numerical
A block of mass $4\text{ kg}$ rests on a surface with $\mu_s = 0.5$. The limiting friction is ($g = 10\text{ m/s}^2$):
A. $2\text{ N}$
B. $40\text{ N}$
C. $20\text{ N}$ ✓ Correct
D. $8\text{ N}$
Solution: $f_{max} = \mu_sN = 0.5 \times 4 \times 10 = 20\text{ N}$.
Q10 — Friction · hard · numerical
For the same block ($\mu_s = 0.5$, $m = 4\text{ kg}$), a horizontal force of $15\text{ N}$ is applied. The frictional force acting is:
A. $5\text{ N}$
B. $15\text{ N}$ ✓ Correct
C. Zero
D. $20\text{ N}$
Solution: Since $15\text{ N}$ is below the limiting value of $20\text{ N}$, the block does not move and static friction exactly balances the applied force.
Q11 — Friction · medium · numerical
A block of mass $10\text{ kg}$ rests on a surface with $\mu = 0.2$. The frictional force when it slides is ($g = 10\text{ m/s}^2$):
A. $2\text{ N}$
B. $100\text{ N}$
C. $20\text{ N}$ ✓ Correct
D. $50\text{ N}$
Solution: $f = \mu mg = 0.2 \times 10 \times 10 = 20\text{ N}$.
Q12 — Friction · medium · numerical
A body slides on a horizontal surface with $\mu = 0.4$. Its retardation is ($g = 10\text{ m/s}^2$):
A. $4\text{ m/s}^2$ ✓ Correct
B. $10\text{ m/s}^2$
C. $2.5\text{ m/s}^2$
D. $0.4\text{ m/s}^2$
Solution: $a = \mu g = 0.4 \times 10 = 4\text{ m/s}^2$, independent of the mass.
Q13 — Friction · hard · numerical
The angle of repose for surfaces with $\mu = 0.5$ is approximately:
A. $60^\circ$
B. $26.6^\circ$ ✓ Correct
C. $30^\circ$
D. $45^\circ$
Solution: $\theta = \tan^{-1}(0.5) \approx 26.6^\circ$.
Q14 — Friction · hard · numerical
A block of mass $5\text{ kg}$ with $\mu = 0.3$ is pulled by a horizontal force of $20\text{ N}$. Its acceleration is ($g = 10\text{ m/s}^2$):
A. $1\text{ m/s}^2$ ✓ Correct
B. $7\text{ m/s}^2$
C. $3\text{ m/s}^2$
D. $4\text{ m/s}^2$
Solution: Friction $= 0.3 \times 50 = 15\text{ N}$, so the net force is $5\text{ N}$ and $a = \dfrac{5}{5} = 1\text{ m/s}^2$.
Q15 — Friction · hard · numerical
A car moving at $10\text{ m/s}$ brakes on a road with $\mu = 0.5$. Its stopping distance is ($g = 10\text{ m/s}^2$):
A. $5\text{ m}$
B. $20\text{ m}$
C. $10\text{ m}$ ✓ Correct
D. $2\text{ m}$
Solution: $d = \dfrac{v^2}{2\mu g} = \dfrac{100}{2 \times 0.5 \times 10} = 10\text{ m}$.
Q16 — Friction · hard · numerical
A car moving at $20\text{ m/s}$ brakes on a road with $\mu = 0.4$. Its stopping distance is ($g = 10\text{ m/s}^2$):
A. $40\text{ m}$
B. $50\text{ m}$ ✓ Correct
C. $100\text{ m}$
D. $25\text{ m}$
Solution: $d = \dfrac{400}{2 \times 0.4 \times 10} = \dfrac{400}{8} = 50\text{ m}$.
Q17 — Friction · medium · numerical
A body just begins to slide on an incline of $45^\circ$. The coefficient of static friction is:
A. $1$ ✓ Correct
B. $1.414$
C. $0.5$
D. $0.707$
Solution: At the angle of repose $\mu = \tan 45^\circ = 1$.
Q18 — Friction · hard · numerical
A block of mass $2\text{ kg}$ rests on an incline of $30^\circ$ with $\mu = 0.5$. The frictional force on it is approximately ($g = 10\text{ m/s}^2$):
A. $10\text{ N}$
B. $5\text{ N}$
C. $8.66\text{ N}$ ✓ Correct
D. $20\text{ N}$
Solution: $f = \mu mg\cos\theta = 0.5 \times 2 \times 10 \times 0.866 \approx 8.66\text{ N}$.
Q19 — Friction · medium · numerical
The minimum horizontal force needed to start a block of mass $m$ moving on a surface of static friction coefficient $\mu_s$ is:
A. $\mu_s m$
B. $\mu_s mg$ ✓ Correct
C. $mg$
D. $\dfrac{mg}{\mu_s}$
Solution: It must just exceed the limiting friction.
Q20 — Friction · medium · numerical
The normal reaction on a block of mass $m$ resting on an incline of angle $\theta$ is:
A. $mg$
B. $mg\tan\theta$
C. $mg\cos\theta$ ✓ Correct
D. $mg\sin\theta$
Solution: Only the component of weight perpendicular to the surface is balanced by the normal reaction.
Q21 — Friction · medium · numerical
The retardation of a sliding body due to friction is independent of:
A. The coefficient of friction
B. Its mass ✓ Correct
C. The acceleration due to gravity
D. The nature of the surfaces
Solution: Since $a = \mu g$, the mass cancels out entirely.