Kinetic Energy — IISER Physics MCQs with Solutions
Free IISER Physics Kinetic Energy MCQs with step-by-step solutions (8 questions). Part of Work, Power and Energy. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Kinetic Energy · easy · theory
Kinetic energy in terms of the momentum p and mass m is:
A. KE = p/2m
B. KE = p²/2m ✓ Correct
C. KE = p²m/2
D. KE = 2m/p²
Solution: KE = ½mv² and p = mv give KE = p²/2m. KE is a scalar and can never be negative.
Q2 — Kinetic Energy · medium · theory
If the momentum of a body is doubled, its kinetic energy becomes:
A. √2 times
B. 2 times
C. 4 times ✓ Correct
D. Unchanged
Solution: KE = p²/2m ∝ p². Doubling p quadruples KE. Trap: doubling KE only raises p by √2.
Q3 — Kinetic Energy · easy · numerical
A 2 kg body moves at 10 m/s. Its kinetic energy is:
A. 20 J
B. 200 J
C. 100 J ✓ Correct
D. 50 J
Solution: KE = ½mv² = ½×2×100 = 100 J.
Q4 — Kinetic Energy · medium · numerical
A body of mass 5 kg has momentum 10 kg·m/s. Its kinetic energy is:
A. 10 J ✓ Correct
B. 50 J
C. 20 J
D. 5 J
Solution: KE = p²/2m = 100/10 = 10 J.
Q5 — Kinetic Energy · hard · numerical
The kinetic energy of a body is increased by 300%. The percentage increase in its momentum is:
A. 300%
B. 100% ✓ Correct
C. 200%
D. 73%
Solution: New KE = 4×old ⇒ p ∝ √KE doubles ⇒ +100%. Trap: 300% increase means ×4, not ×3.
Q6 — Kinetic Energy · medium · numerical
Two bodies of masses 1 kg and 4 kg have equal kinetic energies. The ratio of their momenta p₁ : p₂ is:
A. 1 : 4
B. 1 : 2 ✓ Correct
C. 2 : 1
D. 1 : 16
Solution: p = √(2m·KE) ∝ √m for equal KE ⇒ p₁:p₂ = 1:2.
Q7 — Kinetic Energy · hard · theory
Which statement about kinetic energy is correct?
A. Its value depends on the reference frame of the observer ✓ Correct
B. It can be negative in a moving frame
C. It is the same in all reference frames
D. It is a vector along the velocity
Solution: v differs between frames, so KE = ½mv² is frame-dependent (a passenger has zero KE in the train frame, large KE in the ground frame). It is never negative in any frame.
Q8 — Kinetic Energy · hard · numerical
A stationary body explodes into two fragments of masses m/3 and 2m/3 moving with equal and opposite momenta. The ratio of the kinetic energy of the lighter fragment to the heavier one is:
A. 1 : 2
B. 2 : 1 ✓ Correct
C. 1 : 1
D. 1 : 4
Solution: Equal p ⇒ KE ∝ 1/m ⇒ KE(m/3) : KE(2m/3) = (2m/3) : (m/3) = 2 : 1 — the lighter piece carries more energy.