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Quiz Chapter 3: Gravitation

10 questions · Form 4 Physics Bab 3: Gravitation

Question 1 of 10Score: 0

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

Full Question List & Answer Key

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1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. What is the main application of non-geostationary satellites like TiungSAT and RazakSAT?

  1. Direct-to-home satellite TV broadcast
  2. Earth observation and environmental sensing
  3. 24-hour fixed communications link
  4. Geostationary weather monitoring
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Answer: B

Non-geostationary satellites in lower orbits sweep across different geographical zones, making them ideal for high-resolution Earth imaging and sensing.

7. 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.

8. A planet is at perihelion (closest approach to the Sun). How does its orbital speed compare to when it is at aphelion (furthest distance)?

  1. Orbital speed is maximum at perihelion
  2. Orbital speed is minimum at perihelion
  3. Orbital speed remains constant throughout
  4. Orbital speed becomes zero at perihelion
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Answer: A

By Kepler's Second Law, conservation of angular momentum requires a planet to move fastest at perihelion and slowest at aphelion.

9. 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.

10. 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.

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