Force and Pressure Part 4: MCQs (Q76–Q100)
⚡ Force and Pressure – MCQs for Class 8 Science
Part 4: Q76–Q100
Q76. When a person lies down, pressure on the ground:
A) Increases
B) Decreases
C) Remains same
D) Becomes zero
✅ Correct Answer: B) Decreases
Explanation:
- B) ✔ Larger contact area while lying → less pressure.
- A, C, D – Incorrect.
Q77. If a force of 200 N acts on area 2 m², pressure is:
A) 50 Pa
B) 100 Pa
C) 200 Pa
D) 400 Pa
✅ Correct Answer: B) 100 Pa
Explanation:
- P = F/A = 200 ÷ 2 = 100 Pa.
- B) ✔ Correct calculation.
Q78. Which principle explains why dams are made thicker at the bottom?
A) Pascal’s Law
B) Newton’s Law
C) Archimedes’ Principle
D) Pressure increases with depth
✅ Correct Answer: D) Pressure increases with depth
Explanation:
- D) ✔ More depth = more pressure → stronger base needed.
Q79. The SI unit of thrust is:
A) Pascal
B) Joule
C) Newton
D) Watt
✅ Correct Answer: C) Newton
Explanation:
- Thrust = force applied normally on surface.
- C) ✔ Unit same as force = Newton.
Q80. Force can bring a moving object to rest because:
A) It decreases its weight
B) It increases pressure
C) It changes state of motion
D) It makes object lighter
✅ Correct Answer: C) It changes state of motion
Explanation:
- C) ✔ Force can stop or slow down motion.
Q81. A person applies 40 N force on nail with area 0.01 m². Pressure = ?
A) 40 Pa
B) 400 Pa
C) 4000 Pa
D) 40000 Pa
✅ Correct Answer: D) 40000 Pa
Explanation:
- P = F/A = 40 ÷ 0.01 = 4000 N/m² = 40,000 Pa.
- D) ✔ Correct.
Q82. Which force enables us to walk on ground?
A) Gravitational force
B) Frictional force
C) Muscular force
D) Magnetic force
✅ Correct Answer: B) Frictional force
Explanation:
- B) ✔ Friction between foot and ground allows forward push.
Q83. A cube floats in water because:
A) It is lighter than air
B) Water has no pressure
C) Its density is less than water
D) It is hollow inside
✅ Correct Answer: C) Its density is less than water
Explanation:
- C) ✔ Object floats if density < liquid density.
Q84. Which of these is a unit of force?
A) Pascal
B) Newton
C) Joule
D) Dyne
✅ Correct Answer: B) Newton
Explanation:
- B) ✔ SI unit of force = Newton.
Q85. Why does the tip of a sewing needle easily pierce cloth?
A) It is heavy
B) It has small area
C) It is long
D) It is light
✅ Correct Answer: B) It has small area
Explanation:
- B) ✔ Small area = more pressure = easy piercing.
Q86. Pressure cooker cooks food faster because:
A) It reduces flame
B) It reduces pressure
C) It increases pressure inside
D) It reduces boiling point
✅ Correct Answer: C) It increases pressure inside
Explanation:
- C) ✔ Higher pressure → higher boiling point → faster cooking.
Q87. When you hit a ball, the applied force is:
A) Muscular force
B) Gravitational force
C) Frictional force
D) Electrostatic force
✅ Correct Answer: A) Muscular force
Explanation:
- A) ✔ Hitting uses muscles.
Q88. The pressure exerted by air at a place decreases with:
A) Depth
B) Altitude
C) Density
D) Force
✅ Correct Answer: B) Altitude
Explanation:
- B) ✔ Higher altitude = less air column = less pressure.
Q89. A suction pump works on principle of:
A) Gravity
B) Atmospheric pressure
C) Friction
D) Magnetism
✅ Correct Answer: B) Atmospheric pressure
Explanation:
- B) ✔ Liquid rises because atmospheric pressure pushes it up.
Q90. Which of these is not a force?
A) Push
B) Pull
C) Heat
D) Lift
✅ Correct Answer: C) Heat
Explanation:
- A, B, D – Examples of forces.
- C) ✔ Heat = energy, not force.
Q91. In a hydraulic system, pressure applied is:
A) Reduced in liquid
B) Increased only downward
C) Transmitted equally in all directions
D) Cancelled
✅ Correct Answer: C) Transmitted equally in all directions
Explanation:
- C) ✔ Pascal’s law → pressure transmitted equally.
Q92. Which of these cannot happen due to a force?
A) Changing shape of object
B) Changing mass of object
C) Changing direction of motion
D) Starting motion of object
✅ Correct Answer: B) Changing mass of object
Explanation:
- B) ✔ Mass cannot be changed by force.
Q93. A floating ship displaces water equal to its:
A) Weight
B) Volume
C) Height
D) Area
✅ Correct Answer: A) Weight
Explanation:
- Archimedes’ Principle → buoyant force = weight of displaced fluid.
- A) ✔ Correct.
Q94. What is thrust?
A) Force parallel to surface
B) Force acting normally on surface
C) Force without contact
D) Force due to friction
✅ Correct Answer: B) Force acting normally on surface
Explanation:
- B) ✔ Thrust = perpendicular force.
Q95. Why does a balloon burst when pricked with a needle?
A) Pressure decreases suddenly
B) Pressure increases suddenly
C) Air rushes out
D) Balloon becomes heavy
✅ Correct Answer: C) Air rushes out
Explanation:
- C) ✔ Needle makes hole → air escapes → burst.
Q96. A boat floats on water due to:
A) Gravitational force only
B) Pressure of air
C) Buoyant force of water
D) Weight of boat
✅ Correct Answer: C) Buoyant force of water
Explanation:
- C) ✔ Buoyant force balances weight.
Q97. Which force is responsible for motion of planets around Sun?
A) Magnetic force
B) Gravitational force
C) Electrostatic force
D) Muscular force
✅ Correct Answer: B) Gravitational force
Explanation:
- B) ✔ Gravity keeps planets in orbit.
Q98. An example of non-contact force is:
A) Muscular force
B) Frictional force
C) Gravitational force
D) Normal force
✅ Correct Answer: C) Gravitational force
Explanation:
- C) ✔ Acts without physical contact.
Q99. The shape of airplane wings is based on:
A) Newton’s law
B) Pascal’s law
C) Bernoulli’s principle
D) Archimedes’ principle
✅ Correct Answer: C) Bernoulli’s principle
Explanation:
- C) ✔ Faster air on top = lower pressure → lift.
Q100. Which instrument is used to measure atmospheric pressure?
A) Thermometer
B) Hydrometer
C) Barometer
D) Manometer
✅ Correct Answer: C) Barometer
Explanation:
- A) Temperature.
- B) Density of liquids.
- C) ✔ Barometer = atmospheric pressure.
- D) Gas/liquid pressure in containers.
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