Physics MCQs

Question #681

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The dimensional formula of coefficient of viscosity is

A. [ML⁻¹T⁻¹]

B. [M⁰LT⁻¹]

C. [ML⁻²T]

D. [MLT⁻¹]

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Correct Answer: Option A

Explanation:
Viscosity η = Force/(Area × velocity gradient). Force [MLT⁻²], area [L²], velocity gradient [T⁻¹]. So η = [MLT⁻²]/([L²][T⁻¹]) = [ML⁻¹T⁻¹]. Often asked.

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Question #682

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1 nanometer equals

A. 10⁻⁹ m

B. 10⁻¹⁰ m

C. 10⁻⁶ m

D. 10⁻¹² m

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Correct Answer: Option A

Explanation:
nano = 10⁻⁹. So 1 nm = 10⁻⁹ m. Angstrom = 10⁻¹⁰ m. picometer = 10⁻¹² m.

This question belongs to: Science Physics

Question #683

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The least count of a vernier calliper is 0.01 cm. A measurement should be recorded as

A. 2.500 cm

B. 2.5 cm

C. 2.50 cm

D. 2.5000 cm

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Correct Answer: Option C

Explanation:
Least count determines precision: two decimal places. So 2.50 cm. Extra digits indicate false precision.

This question belongs to: Science Physics

Question #684

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If the percentage error in measurement of radius of a sphere is 2%, the percentage error in volume is

A. 8%

B. 2%

C. 4%

D. 6%

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Correct Answer: Option D

Explanation:
Volume V = (4/3)πr³, so ΔV/V = 3 Δr/r. Percentage error in volume = 3 × 2% = 6%.

This question belongs to: Science Physics

Question #685

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A particle starts from rest and moves with constant acceleration. The distance covered in the first 3 seconds is 9 m. The acceleration is

A. 3 m/s²

B. 1 m/s²

C. 4 m/s²

D. 2 m/s²

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Correct Answer: Option D

Explanation:
s = ut + ½at², u=0 => 9 = ½a(3)² => 9 = ½a×9 => a = 2 m/s².

This question belongs to: Science Physics

Question #686

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The slope of a velocity-time graph gives

A. Displacement

B. Distance

C. Acceleration

D. Speed

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Correct Answer: Option C

Explanation:
Slope = dv/dt = acceleration. Area under v-t gives displacement. Often confused.

This question belongs to: Science Physics

Question #687

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A ball is thrown upward with velocity 30 m/s. Time to reach maximum height (g=10) is

A. 3 s

B. 6 s

C. 1.5 s

D. 2 s

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Correct Answer: Option A

Explanation:
v = u - gt, at top v=0 => t = u/g = 30/10 = 3 s.

This question belongs to: Science Physics

Question #688

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A bus travels the first 20 km at 40 km/h and the next 20 km at 60 km/h. Average speed is

A. 52 km/h

B. 45 km/h

C. 50 km/h

D. 48 km/h

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Correct Answer: Option D

Explanation:
Time1 = 20/40=0.5 h, Time2=20/60=1/3 h. Total time=5/6 h. Total distance=40 km. Avg speed=40/(5/6)=48 km/h. Not arithmetic mean.

This question belongs to: Science Physics

Question #689

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An object moving with uniform circular motion has

A. Constant velocity

B. Constant acceleration

C. Constant displacement

D. Constant speed

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Correct Answer: Option D

Explanation:
Speed constant, velocity and acceleration (centripetal) change direction. KE constant.

This question belongs to: Science Physics

Question #690

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A car decelerates uniformly from 20 m/s to rest in 4 s. Distance covered is

A. 20 m

B. 40 m

C. 80 m

D. 60 m

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Correct Answer: Option B

Explanation:
a = (0-20)/4 = -5 m/s². s = 20×4 + ½(-5)×16 = 80 - 40 = 40 m. Or average velocity 10 m/s × 4 = 40 m.

This question belongs to: Science Physics

Question #691

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Newton's second law gives the measure of

A. Momentum

B. Inertia

C. Energy

D. Force

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Correct Answer: Option D

Explanation:
F = ma, defines force quantitatively. First law inertia, third action-reaction.

This question belongs to: Science Physics

Question #692

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A force of 20 N acts on a body of mass 4 kg for 5 s. Change in momentum is

A. 4 kg m/s

B. 100 kg m/s

C. 80 kg m/s

D. 20 kg m/s

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Correct Answer: Option B

Explanation:
Impulse = F×t = 20×5 = 100 N s = change in momentum.

This question belongs to: Science Physics

Question #693

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If the momentum of a body is doubled, its kinetic energy becomes

A. Same

B. Half

C. Four times

D. Double

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Correct Answer: Option C

Explanation:
K = p²/(2m), if p'=2p, K'=4p²/(2m)=4K. Quadratic relation.

This question belongs to: Science Physics

Question #694

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An iron sphere of mass 10 kg has same diameter as an aluminium sphere of mass 3.5 kg. Both fall from rest in vacuum. Which hits ground first?

A. Aluminium sphere

B. Both together

C. Iron sphere

D. Depends on density

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Correct Answer: Option B

Explanation:
In vacuum, no air resistance, all bodies fall with same g. Galileo's law. Mass independent.

This question belongs to: Science Physics

Question #695

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A bullet of mass 20 g fired from a gun of mass 5 kg with velocity 200 m/s. Recoil velocity of gun is

A. 2 m/s

B. 0.8 m/s

C. 1 m/s

D. 0.4 m/s

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Correct Answer: Option B

Explanation:
Conservation of momentum: 0 = (0.02×200) + (5×v) => v = -4/5 = -0.8 m/s (magnitude 0.8 m/s).

This question belongs to: Science Physics

Question #696

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Work done by a force is zero when the angle between force and displacement is

A. 90°

B. 45°

C. 180°

D. 0°

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Correct Answer: Option A

Explanation:
W = Fd cosθ, cos90° = 0, so work zero. e.g., coolie carrying load horizontally.

This question belongs to: Science Physics

Question #697

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1 kWh of energy equals

A. 3.6 × 10⁶ J

B. 3.6 J

C. 3.6 × 10³ J

D. 3.6 × 10⁸ J

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Correct Answer: Option A

Explanation:
1 kWh = 1000 W × 3600 s = 3.6 × 10⁶ J. Important conversion.

This question belongs to: Science Physics

Question #698

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A 100 W bulb is used for 10 hours. Energy consumed is

A. 1 kWh

B. 10 kWh

C. 0.1 kWh

D. 100 kWh

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Correct Answer: Option A

Explanation:
Energy = 0.1 kW × 10 h = 1 kWh.

This question belongs to: Science Physics

Question #699

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A spring with k=200 N/m is compressed by 0.1 m. Potential energy stored is

A. 20 J

B. 0.5 J

C. 1 J

D. 2 J

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Correct Answer: Option C

Explanation:
U = ½ k x² = ½×200×0.01 = 1 J.

This question belongs to: Science Physics

Question #700

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The gravitational force between two objects of masses 2 kg and 3 kg separated by 2 m (G = 6.67×10⁻¹¹) is

A. 1.0005×10⁻¹⁰ N

B. 6.67×10⁻¹¹ N

C. 1×10⁻¹⁰ N

D. 2×10⁻¹⁰ N

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Correct Answer: Option A

Explanation:
F = G m1 m2 / r² = 6.67×10⁻¹¹ × 6 / 4 = 6.67×10⁻¹¹ × 1.5 = 1.0005×10⁻¹⁰ N.

This question belongs to: Science Physics

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