SSC CGL Science – Work, Energy, Power & Gravitation – Tier II Level · Marathon

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SSC CGL Science – Work, Energy, Power & Gravitation – Tier II Level · Marathon – 12 questions, subject: General Science. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

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1.  
A planet has 9 times the mass of the Earth and 4 times its radius. Its escape velocity is (Earth: 11.2 km/s):

Correct Answer: B [16.8 km/s]

Explanation:

vₑ = √(2GM/R) ∝ √(M/R) = √(9/4) = 1.5 → 1.5 × 11.2 = 16.8 km/s.

2.  
Satellite A has a period of 2 hours. Satellite B orbits the same planet at 9 times A's orbital radius. B's period is:

Correct Answer: C [54 hours]

Explanation:

T ∝ r^(3/2) → 9^(3/2) = 27 → 2 × 27 = 54 h.

3.  
At what depth below the surface is g equal to 3/4 of its surface value? (R = 6400 km)

Correct Answer: A [1600 km]

Explanation:

g(1 − d/R) = 3g/4 → d = R/4 = 1600 km.

4.  
Using g' ≈ g(1 − 2h/R), the height at which g decreases by 1% is about (R = 6400 km):

Correct Answer: B [32 km]

Explanation:

2h/R = 0.01 → h = 0.005 × 6400 = 32 km.

5.  
The ratio of the escape velocity to the orbital velocity of a satellite orbiting close to the Earth's surface is:

Correct Answer: D [√2 : 1]

Explanation:

vₑ = √(2gR), v₀ = √(gR) → ratio √2.

6.  
If the Earth shrank to half its radius with its mass unchanged, the value of g on its surface would become:

Correct Answer: D [4 times]

Explanation:

g = GM/R² → R halved → 4 times.

7.  
If the momentum of a body is doubled (mass unchanged), its kinetic energy becomes:

Correct Answer: C [4 times]

Explanation:

Answer: 4 times. KE = p²/2m → 2² = 4.

8.  
A spring of spring constant 200 N/m is stretched by 0.1 m. The elastic potential energy stored is:

Correct Answer: B [1 J]

Explanation:

Answer: 1 J. ½kx² = ½ × 200 × 0.01 = 1 J.

9.  
Assertion–ReasonAssertion (A): The escape velocity from the Earth is the same for a pebble and for a rocket.
Reason (R): vₑ = √(2GM/R), where M is the mass of the Earth, not of the body.

Correct Answer: A [Both A and R are true and R explains A]

Explanation:

The body's mass cancels in ½mv² = GMm/R.

10.  
Data tableHypothetical planets of one star – orbit radius (AU): 1, 4, 9; period (years): 1, 8, 27. A fourth planet at 16 AU would have a period of:

Correct Answer: B [64 years]

Explanation:

T² = r³ in these units → T = 16^(3/2) = 64 years.

11.  
A truck moves at a steady 20 m/s against a total resisting force of 3000 N. The power delivered by its engine is:

Correct Answer: A [60 kW]

Explanation:

P = F × v = 3000 × 20 = 60,000 W = 60 kW.

12.  
A 3 kg ball at 4 m/s collides with a 1 kg ball at rest and they stick together. The kinetic energy lost is:

Correct Answer: D [6 J]

Explanation:

Common v = 12/4 = 3 m/s; KE 24 J → 18 J; loss 6 J (= 1/4 of 24 J, as M/(m + M) = 1/4).

➤ Full notes, shortcuts and every answer explained – SSC CGL 2026 General Science book (₹149): www.shanmugamiasacademy.in/study-materials/ssc-cgl-general-science

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