🌍 Class 9 – Gravitation MCQ Quiz
Practice universal law of gravitation, free fall, mass & weight, pressure and buoyancy with interactive MCQs.
🧠 Multiple Choice Questions (20)
Tap an option to check your answer. Then use Show Answer, Explanation and Did you know for deeper understanding.
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1. What does the universal law of gravitation state?
Result:
💬 Answer:
The correct option is (B).
📚 Explanation:
Newton’s universal law of gravitation says that any two objects in the universe attract each other with a
force proportional to M × m and inversely proportional to d², where
M and m are the masses and d is the distance between their centres.
✨ Did you know?
This law works for everything – from a falling apple to the motion of planets and even distant galaxies. 🌌
2. Gravitational force between two objects is directly proportional to:
Result:
💬 Answer:
The correct option is (B).
📚 Explanation:
According to the universal law, F ∝ M × m. If either mass increases, the gravitational
force also increases.
✨ Did you know?
The Sun is so massive that it keeps all the planets in orbit through its gravitational pull. ☀️
3. Gravitational force between two objects is inversely proportional to:
Result:
💬 Answer:
The correct option is (B).
📚 Explanation:
The law says F ∝ 1/d², so if distance becomes double, the force becomes only
one-fourth.
✨ Did you know?
This “inverse square law” also appears in light, sound and electric forces. 📉
4. What is the SI unit of the universal gravitational constant G?
Result:
💬 Answer:
The correct option is (A).
📚 Explanation:
From the formula F = G M m / d², rearranging gives the unit of G as
N m² kg⁻².
✨ Did you know?
Henry Cavendish measured G using a very sensitive balance in the 18th century. ⚖️
5. Which of the following remains the same for an object on Earth and on the Moon?
Result:
💬 Answer:
The correct option is (A).
📚 Explanation:
Mass is the amount of matter and does not change with place. Weight depends on g, so it is
different on Earth and Moon.
✨ Did you know?
Astronauts on the Moon weigh less, but their mass (and inertia) remains the same as on Earth. 🚀
6. What do we call the motion of an object when it falls towards Earth under the gravitational force alone?
Result:
💬 Answer:
The correct option is (A).
📚 Explanation:
When only Earth’s gravitational force acts on the object (no air resistance or other forces), the motion is
called free fall.
✨ Did you know?
Astronauts in orbit appear “weightless” because they are in continuous free fall around the Earth. 🛰️
7. What is the approximate value of acceleration due to gravity g on the surface of the Earth?
Result:
💬 Answer:
The correct option is (A).
📚 Explanation:
At Earth’s surface, objects in free fall gain velocity by about 9.8 m s⁻¹ every second.
✨ Did you know?
At high altitudes or at the equator, the value of g is slightly less than at the poles. 🌎
8. Which statement is true about objects in free fall near the Earth (ignoring air resistance)?
Result:
💬 Answer:
The correct option is (A).
📚 Explanation:
From F = m g and F = m a, the acceleration due to gravity g is the same
for all bodies in free fall, so objects fall at the same rate if air resistance is negligible.
✨ Did you know?
On the Moon (without air), a feather and a hammer dropped together hit the ground at the same time. 🪶🔨
9. What is thrust?
Result:
💬 Answer:
The correct option is (A).
📚 Explanation:
When a force acts normal (perpendicular) to a surface, it is called thrust. Pressure is
thrust per unit area.
✨ Did you know?
Rockets move forward due to the powerful thrust produced by burning fuel. 🚀
10. What is buoyant force (upthrust)?
Result:
💬 Answer:
The correct option is (A).
📚 Explanation:
Fluid (liquid or gas) exerts an upward force on an immersed object. If this buoyant force is large enough,
the object can float.
✨ Did you know?
Ships made of iron float because their average density (iron + air inside) is less than that of water. 🚢
11. Two bodies of masses 4 kg and 2 kg are placed 1 m apart. Take G = 6.67×10⁻¹¹ N m² kg⁻². What is the gravitational force between them (approximately)?
Result:
💬 Answer:
Correct option is (A).
📚 Explanation:
Formula: F = G M m / d²
M = 4 kg, m = 2 kg, d = 1 m
F = 6.67×10⁻¹¹ × (4 × 2) / 1² = 6.67×10⁻¹¹ × 8 ≈ 5.34×10⁻¹⁰ N.
M = 4 kg, m = 2 kg, d = 1 m
F = 6.67×10⁻¹¹ × (4 × 2) / 1² = 6.67×10⁻¹¹ × 8 ≈ 5.34×10⁻¹⁰ N.
✨ Did you know?
Gravity between everyday objects is extremely tiny, which is why we don’t notice it. 🔍
12. What is the weight of a 5 kg object on Earth? (Take g = 9.8 m s⁻²)
Result:
💬 Answer:
Correct option is (A).
📚 Explanation:
Formula: W = m g
= 5 kg × 9.8 m s⁻² = 49 N.
= 5 kg × 9.8 m s⁻² = 49 N.
✨ Did you know?
A 5 kg mass would weigh only about 8 N on the Moon because g is much smaller there. 🌙
13. The value of g on the Moon is about 1.6 m s⁻². What is the weight of a 10 kg object on the Moon?
Result:
💬 Answer:
Correct option is (B).
📚 Explanation:
W = m g = 10 × 1.6 = 16 N (approximately).
✨ Did you know?
This is about 1/6 of the weight on Earth, which is why astronauts can hop and jump easily
on the Moon. 🧑🚀
14. An object is dropped from rest and falls freely for 3 s. Take g = 10 m s⁻². What is its speed after 3 s?
Result:
💬 Answer:
Correct option is (C).
📚 Explanation:
Initial velocity u = 0, time t = 3 s, g = 10 m s⁻²
v = u + g t = 0 + 10 × 3 = 30 m s⁻¹.
v = u + g t = 0 + 10 × 3 = 30 m s⁻¹.
✨ Did you know?
In free fall, speed increases linearly with time when g is constant. 📈
15. A stone is dropped from rest and falls freely for 2 s. Take g = 10 m s⁻². What distance does it fall in 2 s?
Result:
💬 Answer:
Correct option is (B).
📚 Explanation:
s = ½ g t² = ½ × 10 × (2)² = 5 × 4 = 20 m.
✨ Did you know?
Distance in free fall is proportional to t², so if time doubles, distance becomes four times. 🔢
16. An object has a weight of 98 N on Earth. (g = 9.8 m s⁻²). What is its mass?
Result:
💬 Answer:
Correct option is (A).
📚 Explanation:
W = m g ⇒ m = W / g = 98 / 9.8 = 10 kg.
✨ Did you know?
In daily life, weighing machines show your weight but we often casually say “my mass is 50 kg”. ⚖️
17. A force of 50 N acts on a surface of area 0.5 m². What is the pressure on the surface?
Result:
💬 Answer:
Correct option is (A).
📚 Explanation:
P = F / A = 50 / 0.5 = 100 N m⁻².
✨ Did you know?
When you lie down instead of standing, your weight spreads over a larger area, so pressure on the ground
decreases. 🧍♂️➡️🛌
18. A solid has mass 40 g and volume 20 cm³. What is its density? Will it float in water? (Density of water = 1 g cm⁻³)
Result:
💬 Answer:
Correct option is (A).
📚 Explanation:
Density = mass / volume = 40 / 20 = 2 g cm⁻³.
Since 2 > 1, the object is denser than water, so it will sink.
Since 2 > 1, the object is denser than water, so it will sink.
✨ Did you know?
Ice has density less than water, so ice cubes float in your drink. 🧊
19. A body displaces water of weight 30 N when fully immersed. What is the magnitude of buoyant force acting on it?
Result:
💬 Answer:
Correct option is (A).
📚 Explanation:
By Archimedes’ principle, buoyant force = weight of displaced fluid = 30 N, acting
upward.
✨ Did you know?
This principle is used in hydrometers to measure the density of liquids. 🌡️
20. At which place will your weight be slightly more, assuming the same mass?
Result:
💬 Answer:
Correct option is (A).
📚 Explanation:
g is slightly greater at the poles and smaller at the equator because Earth is slightly flattened at the
poles and bulged at the equator. More g ⇒ slightly more weight.
✨ Did you know?
The difference is small, but sensitive instruments can measure it. 🌍