Escape Velocity and Motion of Satellite, orbital velocity, time period and energy of satellite: NEET MCQs with Answers

15 free questions on Escape Velocity and Motion of Satellite, orbital velocity, time period and energy of satellite for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

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Question 1

Previous-year question
A satellite in geostationary orbit has an orbital radius approximately: [NEET 2021]
  1. 2.2 × 10⁴ km
  2. 4.2 × 10⁴ km
  3. 8.4 × 10⁴ km
  4. 1.2 × 10⁴ km
Show answer
Answer: (B) 4.2 × 10⁴ km
Explanation: For a geostationary satellite with period T = 24 hours: T² = (4π²/GM)r³. Substituting T = 86,400 s, M = 6 × 10²⁴ kg, G = 6.67 × 10⁻¹¹, we get r ≈ 4.2 × 10⁷ m = 4.2 × 10⁴ km from Earth's center (about 36,000 km above surface).

Question 2

Previous-year question
If a satellite is moved to an orbit of double the radius, its time period will become: [NEET 2024]
  1. 4 times the original period
  2. 2√2 times the original period
  3. 2 times the original period
  4. √2 times the original period
Show answer
Answer: (B) 2√2 times the original period
Explanation: By Kepler's third law, T² ∝ r³. If the radius doubles, T_new²/T_old² = 8, so T_new = √8·T_old = 2√2·T_old.

Question 3

Previous-year question
A projectile is launched from Earth's surface with velocity v = √(3gR), where g is surface gravity and R is Earth's radius. The projectile will: [NEET 2024]
  1. Remain in circular orbit around Earth
  2. Escape Earth's gravitational field
  3. Fall back to Earth after some time
  4. Achieve escape velocity
Show answer
Answer: (B) Escape Earth's gravitational field
Explanation: The escape velocity is v_e = √(2gR). The given velocity v = √(3gR) > √(2gR), so it exceeds escape velocity. Therefore, the projectile has sufficient energy to escape Earth's gravity completely and reach infinity with non-zero velocity.

Question 4

Previous-year question
The escape velocity from Earth is 11.2 km/s. The escape velocity from a planet with twice Earth's mass and twice Earth's radius would be: [NEET 2023]
  1. 11.2 km/s
  2. 5.6 km/s
  3. 22.4 km/s
  4. 15.8 km/s
Show answer
Answer: (A) 11.2 km/s
Explanation: v_e = √(2GM/R). For the planet: v_e' = √(2G·2M/2R) = √(2GM/R) = v_e. When both mass and radius double, the escape velocity remains the same. This shows that escape velocity depends on the ratio M/R, not on the absolute values.

Question 5

Previous-year question
Escape velocity from Earth's surface depends on: [NEET 2024]
  1. The mass of the body being launched
  2. The direction in which the body is launched
  3. The mass and radius of Earth only
  4. The kinetic energy of the body
Show answer
Answer: (C) The mass and radius of Earth only
Explanation: Escape velocity v_e = √(2GM/R), where M is Earth's mass and R is its radius. It is independent of the mass of the escaping body, the launch direction, or any other factor. This universal escape velocity is about 11.2 km/s from Earth's surface.

Question 6

Previous-year question
Satellite orbits at height h = R. To move to height 2R, energy needed: [NEET 2024]
  1. GMm/2R
  2. GMm/3R
  3. GMm/12R
  4. GMm/6R
Show answer
Answer: (C) GMm/12R
Explanation: The total energy in a circular orbit of radius r is −GMm/2r. At h = R, r = 2R and E₁ = −GMm/4R; at h = 2R, r = 3R and E₂ = −GMm/6R. The energy needed is E₂ − E₁ = GMm/4R − GMm/6R = GMm/12R.

Question 7

Previous-year question
Body projected from Earth surface with v = √(2gR). Maximum height: [NEET 2023]
  1. R
  2. 2R
  3. ∞ (escape)
  4. R/2
Show answer
Answer: (C) ∞ (escape)
Explanation: v = √(2gR) = escape velocity. Object reaches infinity with zero velocity. Energy conserved: KE + PE = 0.
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Question 8

Previous-year question
Two satellites A, B at radii r, 2r. Period ratio T_A/T_B: [NEET 2024]
  1. 1/2
  2. 1/√2
  3. 1/2√2
  4. 2√2
Show answer
Answer: (C) 1/2√2
Explanation: T² ∝ r³. T_A²/T_B² = r³/(2r)³ = 1/8. So T_A/T_B = 1/(2√2).

Question 9

Previous-year question
Projectile launched with v = √(3gR) where R = Earth radius, it will: [NEET 2023]
  1. Remain in circular orbit
  2. Escape Earth's field
  3. Fall back to Earth
  4. Achieve escape velocity
Show answer
Answer: (B) Escape Earth's field
Explanation: v_escape = √(2gR). Given v = √(3gR) > √(2gR), so object exceeds escape velocity and escapes.

Question 10

Previous-year question
Geostationary satellite orbital radius approximately: [NEET 2022]
  1. 2.2 × 10⁴ km
  2. 4.2 × 10⁴ km
  3. 8.4 × 10⁴ km
  4. 1.2 × 10⁴ km
Show answer
Answer: (B) 4.2 × 10⁴ km
Explanation: T = 24 hours gives r ≈ 4.2 × 10⁷ m = 42,000 km from center (≈36,000 km altitude). From T² = (4π²/GM)r³.

Question 11

Previous-year question
If satellite moved to orbit of double radius, period becomes: [NEET 2023]
  1. 4 times
  2. 2√2 times
  3. 2 times
  4. √2 times
Show answer
Answer: (B) 2√2 times
Explanation: T² ∝ r³. If r_new = 2r: T_new²/T_old² = 8. Therefore T_new = √8·T_old = 2√2·T_old. Shows orbital dynamics balance.

Question 12

Previous-year question
Geostationary satellite orbital period: [NEET 2024]
  1. 12 hours
  2. 24 hours
  3. 6 hours
  4. 48 hours
Show answer
Answer: (B) 24 hours
Explanation: Orbital period = Earth's rotation period (86,400 s). Keeps satellite fixed above same equatorial point. Orbital radius ≈ 42,164 km.

Question 13

Previous-year question
For a satellite in circular orbit, the orbital velocity v and orbital radius r are related by: [NEET 2024]
  1. v² ∝ r
  2. v² ∝ r²
  3. v² ∝ 1/r
  4. v ∝ r
Show answer
Answer: (C) v² ∝ 1/r
Explanation: For circular orbit, gravitational force provides centripetal force: GMm/r² = mv²/r, giving v² = GM/r. Therefore, v² ∝ 1/r, or v ∝ 1/√r. Satellites closer to the central body move faster.

Question 14

Previous-year question
Escape velocity from planet with double Earth's mass and double Earth's radius: [NEET 2023]
  1. Same as Earth
  2. Twice Earth's
  3. Half Earth's
  4. √2 times Earth's
Show answer
Answer: (A) Same as Earth
Explanation: v_e = √(2GM/R). For planet: v_e' = √(2G·2M/2R) = √(2GM/R) = v_e. When M and R both double, v_e unchanged.

Question 15

Previous-year question
Escape velocity depends on: [NEET 2023]
  1. Mass of escaping object
  2. Mass and radius of planet
  3. Direction of escape
  4. Kinetic energy
Show answer
Answer: (B) Mass and radius of planet
Explanation: v_e = √(2GM/R) depends only on M and R. Independent of object's mass or launch direction. All objects same v_e from Earth.

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