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Quiz Chapter 3: Gravitation

10 questions · Form 4 Physics Bab 3: Gravitation

10 questions · plays in fullscreen

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. A body of mass 2 kg moves in a circle of radius 0.5 m at a constant speed of 4 m s-1. What is the centripetal force required?

  1. 16 N
  2. 64 N
  3. 32 N
  4. 8 N
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Answer: C

F_c = m v² / r = 2 × 4²0.5 = 2 × 160.5 = 642 = 32 N.

2. Which of Kepler's laws states that a planet sweeps out equal areas in equal intervals of time?

  1. Kepler's First Law
  2. Kepler's Third Law
  3. Kepler's Second Law
  4. Newton's First Law
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Answer: C

Kepler's Second Law (Law of Areas) states that a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.

3. If Earth's radius is R, at what height h above Earth's surface is gravitational acceleration equal to g4?

  1. h = R
  2. h = 2R
  3. h = 0.5R
  4. h = 4R
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Answer: A

g ∝ 1r². For g' = g4, the total radius from Earth's centre must double to 2R. Thus r = R + h = 2R => h = R.

4. What provides the centripetal force required to keep a satellite orbiting around the Earth?

  1. Atmospheric pressure
  2. Gravitational force between Earth and satellite
  3. Solar radiation pressure
  4. Magnetic force of the Earth
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Answer: B

The gravitational force exerted by the Earth on the satellite acts as the centripetal force maintaining the circular orbit.

5. Calculated from Earth's surface (M = 5.97 × 1024 kg, R = 6.37 × 106 m, G = 6.67 × 10-11 N m² kg-2, what is Earth's approximate escape velocity?

  1. 7.9 km s-1
  2. 11.2 km s-1
  3. 15.0 km s-1
  4. 9.8 km s-1
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Answer: B

v_e = √[2 × 6.67 × 10-11 × 5.97 × 10246.37 × 106] ≈ 11,180 m s-1 ≈ 11.2 km s-1.

6. Calculate the linear orbital speed of a satellite orbiting Earth at an altitude where distance from Earth's centre is 7.0 × 106 m. (Earth's mass M = 6.0 × 1024 kg, G = 6.67 × 10-11 N m² kg-2

  1. 9.2 × 103 m s-1
  2. 5.7 × 103 m s-1
  3. 7.56 × 103 m s-1
  4. 1.12 × 104 m s-1
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Answer: C

v = √(GM / r) = √[6.67 × 10-11 × 6.0 × 10247.0 × 106] = √5.717 × 107 ≈ 7.56 × 103 m s-1.

7. Why does an astronaut in an orbiting space station experience a feeling of weightlessness?

  1. There is zero gravity in space
  2. The astronaut and space station are in continuous free fall towards Earth
  3. Earth's magnetic field cancels out gravitational force
  4. Centrifugal force completely eliminates mass
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Answer: B

The astronaut and space station fall towards Earth at the same acceleration due to gravity, creating a weightless free-fall environment.

8. What is the shape of planetary orbits around the Sun according to Kepler's First Law?

  1. Hyperbolic
  2. Elliptical
  3. Perfectly circular
  4. Parabolic
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Answer: B

Kepler's First Law states that all planets move in elliptical orbits with the Sun at one focus.

9. Two objects of mass 50 kg and 80 kg are placed 2 m apart. Calculate the gravitational force between them. (G = 6.67 × 10-11 N m² kg-2

  1. 6.67 × 10-8 N
  2. 1.33 × 10-7 N
  3. 6.67 × 10-9 N
  4. 2.67 × 10-8 N
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Answer: A

F = G(m1)m2r² = 6.67 × 10-11 × 50 × 802² = 2.668 × 10-74 = 6.67 × 10-8 N.

10. What is the orbital period of a geostationary satellite?

  1. 12 hours
  2. 48 hours
  3. 24 hours
  4. 365 days
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Answer: C

A geostationary satellite has an orbital period identical to Earth's rotation period, which is 24 hours.

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