Gravitation Part 3: MCQs (Q51–Q75)
🌍 Gravitation – Class 9 Science MCQs
Section 3: Mass, Weight, Thrust & Pressure (Q51–Q75)
Q51. Mass of a body is the measure of its:
A. Force
B. Weight
C. Inertia
D. Density
✅ Correct Answer: C. Inertia
Explanation:
- A. Wrong, force is interaction.
- B. Weight = force due to gravity.
- C. Correct, mass measures resistance to change of motion.
- D. Density = mass/volume.
Q52. Weight of an object is given by:
A. W = mg
B. W = mv
C. W = ma²
D. W = pV
✅ Correct Answer: A. W = mg
Explanation:
- Weight is gravitational force → mass × acceleration due to gravity.
Q53. SI unit of weight is:
A. kg
B. Newton
C. g
D. Pascal
✅ Correct Answer: B. Newton
Explanation:
- Mass in kg × g → force unit = N.
Q54. Mass of body is constant everywhere. Weight changes because:
A. Value of g changes
B. Mass changes
C. Shape changes
D. Density changes
✅ Correct Answer: A. Value of g changes
Q55. A body weighs 600 N on Earth. Weight on Moon = ? (gMoon = 1/6 gEarth)
A. 600 N
B. 300 N
C. 100 N
D. 1200 N
✅ Correct Answer: C. 100 N
Explanation:
- Weight on Moon = (1/6) × 600 = 100 N.
Q56. Mass of body on Moon compared to Earth is:
A. More
B. Less
C. Same
D. Zero
✅ Correct Answer: C. Same
Explanation:
- Mass is universal property, does not change.
Q57. Which is scalar quantity?
A. Weight
B. Force
C. Mass
D. Velocity
✅ Correct Answer: C. Mass
Explanation:
- Mass has magnitude only. Others are vectors.
Q58. Pressure is defined as:
A. Force × Area
B. Force/Area
C. Force × Distance
D. Force × Time
✅ Correct Answer: B. Force/Area
Q59. SI unit of pressure is:
A. Pascal
B. Joule
C. Newton
D. Watt
✅ Correct Answer: A. Pascal
Explanation:
- 1 Pa = 1 N/m².
Q60. For same force, pressure is greater when:
A. Area is smaller
B. Area is larger
C. Mass is larger
D. Height is greater
✅ Correct Answer: A. Area is smaller
Q61. A sharp knife cuts better than blunt one because:
A. More force
B. Less area of contact
C. Friction increases
D. Both A & B
✅ Correct Answer: B. Less area of contact
Explanation:
- Pressure = Force/Area → small area → higher pressure.
Q62. Thrust is defined as:
A. Force per unit area
B. Force acting normally on surface
C. Pressure × area
D. Weight per unit area
✅ Correct Answer: B. Force acting normally on surface
Q63. SI unit of thrust is:
A. Pascal
B. Newton
C. N/m²
D. Joule
✅ Correct Answer: B. Newton
Q64. Pressure on a surface increases when:
A. Force increases
B. Area decreases
C. Both A & B
D. None
✅ Correct Answer: C. Both A & B
Q65. A woman wearing high heels exerts:
A. Less pressure
B. More pressure
C. Same pressure
D. Zero pressure
✅ Correct Answer: B. More pressure
Explanation:
- Small area of contact → high pressure.
Q66. A porter carries luggage on his head. Pressure acts:
A. Parallel to head
B. Normal to head
C. At an angle
D. Zero
✅ Correct Answer: B. Normal to head
Q67. A broad foundation of building is provided to:
A. Increase thrust
B. Decrease thrust
C. Decrease pressure
D. Increase pressure
✅ Correct Answer: C. Decrease pressure
Explanation:
- Large area → small pressure on soil.
Q68. Weight of object immersed in fluid is less than in air because of:
A. Pressure
B. Thrust
C. Buoyant force
D. Viscosity
✅ Correct Answer: C. Buoyant force
Q69. The pressure at depth h in fluid of density ρ is:
A. p = ρgh
B. p = ρg/h
C. p = ρh/g
D. p = h/ρg
✅ Correct Answer: A. p = ρgh
Q70. SI unit of density is:
A. g/cm³
B. kg/m³
C. N/m²
D. J/m³
✅ Correct Answer: B. kg/m³
Q71. Density is defined as:
A. Mass × volume
B. Mass/volume
C. Volume/mass
D. Mass × area
✅ Correct Answer: B. Mass/volume
Q72. If mass = 200 g and volume = 50 cm³, density = ?
A. 2 g/cm³
B. 3 g/cm³
C. 4 g/cm³
D. 5 g/cm³
✅ Correct Answer: C. 4 g/cm³
Explanation:
- Density = m/V = 200/50 = 4.
Q73. Weight is a:
A. Vector quantity
B. Scalar quantity
C. Dimensionless
D. Constant
✅ Correct Answer: A. Vector quantity
Explanation:
- Weight has both magnitude and direction (towards Earth’s centre).
Q74. Which of the following quantities changes from place to place?
A. Mass
B. Weight
C. Density
D. Inertia
✅ Correct Answer: B. Weight
Q75. Two persons of different masses jump from same height. Neglecting air resistance, which hits ground first?
A. Heavier one
B. Lighter one
C. Both together
D. Cannot be said
✅ Correct Answer: C. Both together
Explanation:
- Free fall acceleration g is same for all bodies.
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