If momentum of a body increases by 100%, kinetic energy increases by MCQ with Answer and Explanation

If momentum of a body increases by 100%, kinetic energy increases by
A. 300%
B. 400%
C. 200%
D. 100%
Answer: Option A
Solution (By JKExamLibrary)
KE = p²/2m. If p → 2p, KE' = 4KE, increase = 3KE = 300%. Frequently asked.

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Question #1
A capacitor of capacitance C is charged to voltage V. The energy stored is:
A. ½C/V
B. ½CV²
C. CV²
D. CV

Correct Answer: Option B


Explanation:
Energy stored in capacitor U = ½CV² = ½QV = Q²/(2C). This derives from work done to charge the capacitor against increasing voltage. Option A has wrong dimensions (energy should be joules, CV is coulomb-volt = joule, but missing factor ½); C and D are dimensionally incorrect. Memory tip: 'Capacitor energy = ½CV², analogous to spring energy ½kx²'. This formula-based question tests electrostatics knowledge, frequently appearing in competitive exams. Always recall the three equivalent forms and choose based on given quantities.

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Question #2
Young's double slit: fringe width β = λD/d. If d doubled, β becomes:
A. Half
B. Double
C. Same
D. Four times

Correct Answer: Option A


Explanation:
β ∝ 1/d. If d' = 2d, β' = β/2. Fringe width decreases with increased slit separation. Memory aid: 'β ∝ 1/d; wider slit separation ⇒ narrower fringes'. Wave optics proportionality frequently tested in competitive exams.

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Question #3
Which of the following graphs represents a body at rest?
A. Displacement-time graph parallel to time axis
B. Velocity-time graph with positive slope
C. Displacement-time graph with constant positive slope
D. Velocity-time graph with zero slope

Correct Answer: Option A


Explanation:
For a body at rest, displacement remains constant over time. The displacement-time graph is a horizontal line, parallel to time axis, indicating zero slope (velocity = 0). Option A indicates constant velocity. Option B (velocity-time zero slope) means constant velocity, not necessarily rest (could be constant non-zero velocity). Option D indicates acceleration. So C is correct.

This question belongs to: Science Physics