Practice Library
All MCQs
Browse exam-wise, subject-wise, and country-wise MCQs with explanations.
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Correct Answer: B. The total momentum of an isolated system remains constant
Explanation:
In an isolated system, internal forces occur in equal and opposite pairs, so total momentum is constant.
Correct Answer: 12
Explanation:
Wave speed v=fλ=3×4=12 m/s.
Correct Answer: 3.75
Explanation:
Ohm’s law gives I=V/R=15/4=3.750 A.
Correct Answer: 22.5
Explanation:
K=½mv²=½×5×3²=22.5 J.
Correct Answer: 9
Explanation:
Newton’s second law gives F=ma=3×3=9 N.
Correct Answer: 25.45
Explanation:
Speed=distance/time=280/11=25.45 m/s.
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Correct Answer: C. The half-life is the time for the number of undecayed nuclei to fall to half its initial value
Explanation:
Half-life is a characteristic decay time at which the undecayed population becomes one half.
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Correct Answer: D. A convex lens can converge parallel rays to a real focus
Explanation:
A convex lens is converging and brings parallel incident rays toward its principal focus.
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Correct Answer: A. The electric field points in the direction a positive test charge would accelerate
Explanation:
Electric-field direction is defined by the force direction on a positive test charge.
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Correct Answer: A. It is perpendicular to the direction of wave propagation
Explanation:
A transverse wave oscillates perpendicular to the direction in which the wave travels.
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Correct Answer: B. The total momentum of an isolated system remains constant
Explanation:
In an isolated system, internal forces occur in equal and opposite pairs, so total momentum is constant.
Correct Answer: 6
Explanation:
Wave speed v=fλ=2×3=6 m/s.
