Gravitation is the force of attraction between any two masses in the universe. This chapter explains Newton’s law of universal gravitation, gravitational field strength, acceleration due to gravity, free fall, mass and weight, and the factors affecting gravity. It also covers the motion of planets and satellites, and the applications of gravitational concepts in everyday life. The MCQs below help students assess their understanding of these topics.
1. Who proposed the law of universal gravitation?
- A. Isaac Newton ✅
- B. Albert Einstein
- C. Galileo Galilei
- D. Johannes Kepler
Explanation: Newton formulated the law of universal gravitation in the 17th century.
2. The law of gravitation states that the force between two bodies is:
- A. Directly proportional to the product of their masses ✅
- B. Directly proportional to the sum of their masses
- C. Inversely proportional to the square of their masses
- D. Independent of distance
Explanation: F ∝ m₁m₂ and inversely proportional to the square of the distance between them.
3. The SI unit of the gravitational constant (G) is:
- A. N·m²/kg² ✅
- B. N·m/kg
- C. m/s²
- D. N/kg
Explanation: G is measured in newton meter² per kilogram².
4. The value of G is:
- A. 6.67 × 10⁻¹¹ N·m²/kg² ✅
- B. 9.8 m/s²
- C. 3 × 10⁸ m/s
- D. 1.6 × 10⁻¹⁹ C
Explanation: G has a constant value of 6.67 × 10⁻¹¹ N·m²/kg².
5. Acceleration due to gravity on Earth is approximately:
- A. 9.8 m/s² ✅
- B. 10 m/s²
- C. 6.67 m/s²
- D. 8.9 m/s²
Explanation: The average value of g on Earth’s surface is 9.8 m/s².
6. Which factor does NOT affect the value of g?
- A. Mass of the object ✅
- B. Altitude
- C. Latitude
- D. Depth below the surface
Explanation: g is independent of the object’s mass.
7. Free fall occurs when:
- A. Only gravity acts on the body ✅
- B. Gravity and air resistance act together
- C. No force acts
- D. The body moves at constant velocity
Explanation: In free fall, only gravitational force influences motion.
8. Weight is defined as:
- A. Mass × acceleration due to gravity ✅
- B. Mass × velocity
- C. Mass × distance
- D. Force × area
Explanation: W = mg, measured in newtons.
9. The weight of a body on the Moon is about:
- A. One-sixth of its weight on Earth ✅
- B. Half of its weight on Earth
- C. Twice its weight on Earth
- D. The same as on Earth
Explanation: Moon’s gravity is about 1/6th of Earth’s.
10. Which quantity remains constant everywhere?
- A. Mass ✅
- B. Weight
- C. g
- D. Force
Explanation: Mass does not change with location.
11. The path of a satellite around Earth is:
- A. Elliptical ✅
- B. Circular only
- C. Straight
- D. Irregular
Explanation: Satellites follow elliptical orbits due to gravitational forces.
12. Who measured the value of G experimentally?
- A. Henry Cavendish ✅
- B. Galileo Galilei
- C. Kepler
- D. Newton
Explanation: Cavendish measured G using a torsion balance in 1798.
13. The escape velocity from Earth is about:
- A. 11.2 km/s ✅
- B. 9.8 km/s
- C. 7.9 km/s
- D. 15 km/s
Explanation: Escape velocity is the speed needed to leave Earth’s gravitational field without further propulsion.
14. Which of the following is a field force?
- A. Gravitational force ✅
- B. Frictional force
- C. Tension
- D. Normal force
Explanation: Gravitational force acts without physical contact between bodies.
15. Kepler’s laws are related to:
- A. Planetary motion ✅
- B. Falling bodies
- C. Tides
- D. Weight
Explanation: Kepler’s laws describe the motion of planets under gravitational attraction.