⚡ Force and Pressure – MCQs for Class 8 Science

Part 3: Q51–Q75

Q51. Pressure is measured in:

A) N
B) N/m²
C) Joule
D) Watt

✅ Correct Answer: B) N/m²

Explanation:

• A) N = force.
• B) ✔ N/m² = Pascal = pressure unit.
• C) Joule = work.
• D) Watt = power.

Q52. Which of these is NOT a contact force?

A) Friction
B) Normal reaction
C) Muscular force
D) Gravitational force

✅ Correct Answer: D) Gravitational force

Explanation:

• A, B, C – Require contact.
• D) ✔ Gravity is a non-contact force.

Q53. An object will float in water if:

A) Its density is more than water
B) Its density is less than water
C) Its shape is round
D) It is very heavy

✅ Correct Answer: B) Its density is less than water

Explanation:

• A, D – Object sinks.
• B) ✔ Density < water → float.
• C – Shape doesn’t decide alone.

Q54. The pressure inside liquid increases if:

A) Depth decreases
B) Depth increases
C) Density decreases
D) Gravity decreases

✅ Correct Answer: B) Depth increases

Explanation:

• P = hρg.
• B) ✔ Greater depth → higher pressure.

Q55. The SI unit of pressure is named after:

A) Newton
B) Pascal
C) Joule
D) Boyle

✅ Correct Answer: B) Pascal

Explanation:

• A, C, D – Names for other units or laws.
• B) ✔ Pascal (Blaise Pascal) gave law of fluid pressure.

Q56. Which force opposes motion between two surfaces?

A) Gravitational force
B) Frictional force
C) Magnetic force
D) Muscular force

✅ Correct Answer: B) Frictional force

Explanation:

• A, C, D – Not opposing surface motion.
• B) ✔ Friction resists sliding motion.

Q57. The pressure of liquid at a point depends on:

A) Depth of liquid
B) Density of liquid
C) Gravitational acceleration
D) All of these

✅ Correct Answer: D) All of these

Explanation:

• P = hρg.
• D) ✔ Depth, density, gravity all affect pressure.

Q58. The rise of water in a straw is due to:

A) Friction
B) Gravity
C) Atmospheric pressure
D) Capillary action only

✅ Correct Answer: C) Atmospheric pressure

Explanation:

• A, B – Not main reason.
• C) ✔ Suction lowers pressure → air pressure pushes liquid up.
• D) Capillarity plays minor role, not main cause.

Q59. A heavy truck exerts less pressure on road because:

A) It is very slow
B) It has many wheels
C) It is heavy
D) It moves carefully

✅ Correct Answer: B) It has many wheels

Explanation:

• B) ✔ Large area of tyres distributes weight → less pressure.

Q60. Liquids exert pressure in which direction?

A) Downward only
B) Upward only
C) Sideways only
D) All directions

✅ Correct Answer: D) All directions

Explanation:

• D) ✔ Fluids exert pressure in all directions (Pascal’s law).

Q61. The force with which air pushes an object is called:

A) Muscular force
B) Frictional force
C) Atmospheric pressure
D) Contact force

✅ Correct Answer: C) Atmospheric pressure

Explanation:

• C) ✔ Air exerts atmospheric pressure on objects.

Q62. The pressure at sea level is equal to height of mercury column of:

A) 76 mm
B) 76 cm
C) 100 cm
D) 1 m

✅ Correct Answer: B) 76 cm

Explanation:

• 1 atm = 76 cm Hg = 101,325 Pa.
• B) ✔ Correct standard pressure.

Q63. Which of the following is a non-contact force?

A) Friction
B) Magnetic force
C) Muscular force
D) Normal force

✅ Correct Answer: B) Magnetic force

Explanation:

• B) ✔ Acts without contact.
• A, C, D – Need contact.

Q64. When two forces act in the same direction, net force is:

A) Sum of forces
B) Difference of forces
C) Zero
D) Negative

✅ Correct Answer: A) Sum of forces

Explanation:

• A) ✔ Forces add up if same direction.

Q65. Pressure in a fluid does not depend on:

A) Shape of container
B) Depth of fluid
C) Density of fluid
D) Value of g

✅ Correct Answer: A) Shape of container

Explanation:

• Pressure depends only on h, ρ, g.
• A) ✔ Shape has no effect.

Q66. An example of muscular force is:

A) Lifting a book
B) Falling of stone
C) Attraction of magnet
D) Running water

✅ Correct Answer: A) Lifting a book

Explanation:

• A) ✔ Involves muscle work.
• B, C, D – Other forces.

Q67. Which instrument measures liquid pressure in pipes?

A) Hydrometer
B) Manometer
C) Barometer
D) Thermometer

✅ Correct Answer: B) Manometer

Explanation:

• B) ✔ Manometer → liquid/gas pressure.
• A, C, D – Different uses.

Q68. A fruit falling from tree is due to:

A) Friction
B) Muscular force
C) Gravitational force
D) Air pressure

✅ Correct Answer: C) Gravitational force

Explanation:

• C) ✔ Gravity pulls fruit downward.

Q69. The upward force exerted by liquid on a body is called:

A) Thrust
B) Buoyant force
C) Reaction force
D) Normal force

✅ Correct Answer: B) Buoyant force

Explanation:

• B) ✔ Buoyant force = upthrust in liquids.

Q70. A parachute works on principle of:

A) Reducing area
B) Increasing pressure
C) Increasing surface area to reduce pressure
D) Using muscular force

✅ Correct Answer: C) Increasing surface area to reduce pressure

Explanation:

• C) ✔ Larger area → less pressure → slower fall.

Q71. Which is NOT an example of pressure in daily life?

A) Camel’s broad feet
B) Knife cutting vegetables
C) Ball rolling on ground
D) Tractor’s broad tyres

✅ Correct Answer: C) Ball rolling on ground

Explanation:

• A, B, D – Pressure-based examples.
• C) ✔ Rolling is motion, not pressure application.

Q72. A person applies 50 N force on box. If contact area is 0.5 m², pressure = ?

A) 25 Pa
B) 50 Pa
C) 100 Pa
D) 150 Pa

✅ Correct Answer: C) 100 Pa

Explanation:

• P = F/A = 50 ÷ 0.5 = 100 Pa.
• C) ✔ Correct calculation.

Q73. Which force pulls iron nails towards a magnet?

A) Electrostatic force
B) Gravitational force
C) Magnetic force
D) Muscular force

✅ Correct Answer: C) Magnetic force

Explanation:

• C) ✔ Magnetism attracts iron nails.

Q74. Which law explains transmission of pressure in hydraulic machines?

A) Newton’s First Law
B) Pascal’s Law
C) Archimedes’ Principle
D) Boyle’s Law

✅ Correct Answer: B) Pascal’s Law

Explanation:

• B) ✔ Pascal’s law = pressure equal in all directions in fluids.

Q75. The pressure exerted by atmosphere on unit area is due to:

A) Air above the surface
B) Water vapour
C) Clouds
D) Sunlight

✅ Correct Answer: A) Air above the surface

Explanation:

• A) ✔ Atmosphere weight exerts pressure.
• B, C, D – Minor effects.

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