The escape velocity from a planet depends on: MCQ with Answer and Explanation

The escape velocity from a planet depends on:
A. Radius of the planet only
B. Mass of the escaping body
C. Both mass and radius of the planet
D. Temperature of the planet
Answer: Option C
Solution (By JKSSB Mock Tests)
Escape velocity v_e = √(2GM/R), where M is planet mass, R its radius. Thus v_e depends on both M and R. It is independent of the escaping body's mass (as gravitational and inertial mass cancel). Memory tip: 'v_e ∝ √(M/R); larger M or smaller R ⇒ higher escape velocity'. This gravitation formula application is frequently tested in competitive exams. Always recall that escape velocity is a property of the planet, not the projectile. This problem assesses understanding of gravitational potential energy concepts.

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Practice More Physics Questions

Question #1
The unit of electric power is
A. Joule
B. Ohm
C. Watt
D. Ampere

Correct Answer: Option C


Explanation:
Watt (W) = J/s = V×A. Commercial unit kilowatt-hour (energy). Joule is energy. Ohm resistance. Ampere current.

This question belongs to: Science Physics
Question #2
The work function of a metal is 2.3 eV. The threshold frequency for photoelectric emission is approximately: (h = 4.14×10⁻¹⁵ eV·s)
A. 5.6×10¹⁴ Hz
B. 1.2×10¹⁵ Hz
C. 3.5×10¹⁴ Hz
D. 8.0×10¹⁴ Hz

Correct Answer: Option A


Explanation:
Photoelectric equation: work function φ = hν₀, where ν₀ is threshold frequency. Thus ν₀ = φ/h = 2.3 eV / (4.14×10⁻¹⁵ eV·s) ≈ 5.555×10¹⁴ Hz ≈ 5.6×10¹⁴ Hz. This direct application tests photoelectric effect fundamentals. Memory aid: 'ν₀ = φ/h; higher work function ⇒ higher threshold frequency'. Competitive exams frequently provide h in eV·s for such calculations. Always ensure units match: eV for φ and h to avoid conversion errors. This problem assesses numerical proficiency in modern physics applications.

This question belongs to: Science Physics
Question #3
Which of the following is an example of the Doppler effect?
A. Bending of light around corners
B. Fusion of nuclei
C. Change in frequency of siren as ambulance passes
D. Echo of sound

Correct Answer: Option C


Explanation:
Doppler effect: apparent change in frequency due to relative motion. Siren pitch changes as it approaches/recedes. Echo is reflection. Bending is diffraction. Fusion is nuclear reaction.

This question belongs to: Science Physics