Physics MCQs

Question #1101

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A machine gun fires n bullets per second, each of mass m with velocity v. The force on the gun is

A. nmv/t

B. ½ nmv

C. nmv²

D. nmv

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Correct Answer: Option D

Explanation:
Force = rate of change of momentum = n × (mv) = nmv. This is average force required to hold gun.

This question belongs to: Science Physics

Question #1102

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The work done in moving a body along a closed path in a conservative force field is

A. Minimum

B. Depends on path

C. Zero

D. Maximum

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Correct Answer: Option C

Explanation:
Conservative forces (gravitational, electrostatic) have zero net work around closed path. Friction is non-conservative.

This question belongs to: Science Physics

Question #1103

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A spring of spring constant k is cut into four equal parts. The spring constant of each part is

A. k/4

B. k

C. 2k

D. 4k

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Correct Answer: Option D

Explanation:
For a spring, k ∝ 1/length. So quarter length has 4 times k. Each part has constant 4k.

This question belongs to: Science Physics

Question #1104

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A man pushes a wall but fails to move it. He does

A. Maximum work

B. Negative work

C. Zero work

D. Positive work

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Correct Answer: Option C

Explanation:
Work = force × displacement in direction of force. Displacement zero, so work zero. Physiology work is done internally, but physics work zero.

This question belongs to: Science Physics

Question #1105

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A body of mass 4 kg is raised from height 2 m to 8 m. Increase in potential energy (g=10) is

A. 80 J

B. 320 J

C. 400 J

D. 240 J

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Correct Answer: Option D

Explanation:
ΔPE = mgΔh = 4×10×(8-2) = 4×10×6 = 240 J.

This question belongs to: Science Physics

Question #1106

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If momentum of a body increases by 100%, kinetic energy increases by

A. 100%

B. 300%

C. 200%

D. 400%

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Correct Answer: Option B

Explanation:
KE = p²/2m. If p → 2p, KE' = 4KE, increase = 3KE = 300%. Frequently asked.

This question belongs to: Science Physics

Question #1107

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The gravitational force between two masses is F. If the distance is tripled, force becomes

A. 3F

B. 9F

C. F/3

D. F/9

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Correct Answer: Option D

Explanation:
F ∝ 1/r², so if r→3r, F→F/9.

This question belongs to: Science Physics

Question #1108

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Escape velocity from a planet of mass M and radius R is v. For another planet of mass 4M and radius 2R, escape velocity is

A. √2 v

B. v

C. v/√2

D. 2v

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Correct Answer: Option A

Explanation:
v_esc ∝ √(M/R). New ∝ √(4M/2R) = √(2M/R) = √2 √(M/R) = √2 v.

This question belongs to: Science Physics

Question #1109

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A satellite is orbiting close to Earth's surface. Its orbital speed is (g = 10 m/s², R = 6400 km)

A. 11.2 km/s

B. 4 km/s

C. 16 km/s

D. 8 km/s

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Correct Answer: Option D

Explanation:
v = √(gR) = √(10×6400×10³) = √(64×10⁶) = 8×10³ m/s = 8 km/s. Escape velocity 11.2 km/s.

This question belongs to: Science Physics

Question #1110

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A person weighs 60 kg on Earth. His weight on moon will be (g_moon = g/6)

A. 6 kg

B. 360 kg

C. 10 kg

D. 60 kg

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Correct Answer: Option C

Explanation:
Weight = mg. On moon, weight = 60×(g/6)/g = 10 kg wt. Mass remains 60 kg, but weight is 10 kg force.

This question belongs to: Science Physics

Question #1111

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Atmospheric pressure at sea level is about

A. 10⁵ Pa

B. 10⁹ Pa

C. 10³ Pa

D. 10⁷ Pa

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Correct Answer: Option A

Explanation:
1 atm = 1.013×10⁵ Pa. Standard approximation.

This question belongs to: Science Physics

Question #1112

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A hydraulic press has area ratio 10:1. A force of 20 N on small piston can lift load of

A. 2000 N

B. 200 N

C. 2 N

D. 20 N

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Correct Answer: Option B

Explanation:
Pascal's law: F₁/A₁ = F₂/A₂ => F₂ = (A₂/A₁) F₁ = 10×20 = 200 N.

This question belongs to: Science Physics

Question #1113

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A body of volume 100 cc weighs 80 g in air. It will float in water with

A. 20 cc above water

B. 80 cc submerged

C. It will sink

D. 100 cc submerged

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Correct Answer: Option B

Explanation:
Density = 80/100 = 0.8 g/cc. Water density 1 g/cc. Fraction submerged = 0.8, so 80 cc submerged, 20 cc above. So option B correct.

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Question #1114

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The buoyant force on a body immersed in a fluid depends on

A. Both B and C

B. Acceleration due to gravity

C. Density of body

D. Volume of body

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Correct Answer: Option A

Explanation:
Buoyant force = weight of displaced fluid = (volume of body submerged) × density_fluid × g. Depends on volume displaced and g. Not density of body.

This question belongs to: Science Physics

Question #1115

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A piece of ice floats in a glass of water filled to brim. When ice melts, water level

A. Decreases

B. Increases

C. Remains same

D. First decreases then increases

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Correct Answer: Option C

Explanation:
Ice displaces water equal to its weight. When melted, it occupies exactly that volume. So level unchanged. Classic question.

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Question #1116

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The instrument used to measure pressure difference is

A. Lactometer

B. Barometer

C. Manometer

D. Hydrometer

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Correct Answer: Option C

Explanation:
Manometer measures pressure difference. Barometer atmospheric pressure.

This question belongs to: Science Physics

Question #1117

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Which of the following has the highest specific heat capacity?

A. Copper

B. Water

C. Iron

D. Lead

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Correct Answer: Option B

Explanation:
Water 4200 J/kg°C, used as coolant. Iron ~450, copper ~385, lead ~128.

This question belongs to: Science Physics

Question #1118

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The amount of heat required to convert 1 g of ice at 0°C to water at 0°C is called

A. Latent heat of fusion

B. Specific heat

C. Latent heat of vaporisation

D. Heat capacity

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Correct Answer: Option A

Explanation:
Latent heat of fusion of ice = 80 cal/g = 336 J/g.

This question belongs to: Science Physics

Question #1119

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A bimetallic strip is made of brass and invar. On heating, it bends with brass on

A. No bending

B. Depends on thickness

C. Outer side

D. Inner side

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Correct Answer: Option C

Explanation:
Brass expands more than invar. So it becomes longer, forcing strip to bend with brass on convex (outer) side.

This question belongs to: Science Physics

Question #1120

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Heat from the Sun reaches Earth by

A. Radiation

B. Convection

C. Conduction

D. Evaporation

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Correct Answer: Option A

Explanation:
Vacuum of space, only radiation (electromagnetic waves) can transfer heat.

This question belongs to: Science Physics

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