The kinetic energy of a body is increased by 300%. The percentage increase in its momentum is: MCQ with Answer and Explanation

The kinetic energy of a body is increased by 300%. The percentage increase in its momentum is:
A. 200%
B. 100%
C. 400%
D. 300%
Answer: Option B
Solution (By JKExamLibrary)
KE ∝ p² (since KE = p²/(2m)). If KE increases by 300%, new KE = 4× original KE. Thus p_new² / p_original² = 4 ⇒ p_new / p_original = 2 ⇒ momentum doubles, i.e., 100% increase. Memory tip: 'KE ∝ p²; so %Δp = ½ %ΔKE for small changes, but for large changes use ratio'. This proportional reasoning problem tests energy-momentum relationship, frequently appearing in competitive exams. Always derive from fundamental relations when percentages are large; linear approximations fail here.

This question belongs to: Science Physics

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Question #1 Report Error
A Wheatstone bridge is said to be completely balanced when:
A. Current through the galvanometer is maximum.
B. All four resistors have exactly identical values.
C. The battery supplies zero current.
D. Potential difference across the galvanometer is zero.

Correct Answer: Option D


Explanation:
A Wheatstone bridge circuit consists of four arms with resistances P, Q, R, S and a galvanometer in the middle. It is balanced when no current flows through the galvanometer arm. This happens exclusively when the potentials at the two ends of the galvanometer are equal, meaning the potential difference across it is exactly zero (P/Q = R/S).

This question belongs to: Science Physics
Question #2 Report Error
The root mean square value of alternating current is defined as the equivalent DC current that produces the same:
A. Voltage
B. Power dissipation
C. Magnetic field
D. Charge flow

Correct Answer: Option B


Explanation:
RMS value of AC is defined such that I_rms²R = average power dissipated, same as DC current I_dc would produce (I_dc²R). Thus I_rms = I₀/√2 for sinusoidal AC. This definition ensures power calculations use RMS values. Memory tip: 'RMS: heating effect equivalent to DC; I_rms = 0.707 I₀ for sine wave'. This AC fundamentals concept is frequently tested in competitive exams. Always use RMS values for power calculations in AC circuits; peak values overestimate power.

This question belongs to: Science Physics
Question #3 Report Error
The time period of a simple pendulum is 2 s at a place where g=9.8 m/s². Its length is about
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B. 0.25 m
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D. 0.5 m

Correct Answer: Option A


Explanation:
T=2π√(L/g) => L = gT²/(4π²) ≈ (9.8×4)/(4×9.87) ≈ 1 m.

This question belongs to: Science Physics