Which scientist discovered the laws of planetary motion? MCQ with Answer and Explanation
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Question #1
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Newton's first law defines:
Correct Answer: Option C
Explanation:
Newton's first law (law of inertia) states bodies remain at rest or uniform motion unless acted upon by external force. This defines inertia - resistance to change in motion state. Force is defined in second law; momentum conservation in third. Memory aid: 'First law = inertia; second = F=ma; third = action-reaction'. Fundamental concept frequently tested to assess basic mechanics understanding.
Newton's first law (law of inertia) states bodies remain at rest or uniform motion unless acted upon by external force. This defines inertia - resistance to change in motion state. Force is defined in second law; momentum conservation in third. Memory aid: 'First law = inertia; second = F=ma; third = action-reaction'. Fundamental concept frequently tested to assess basic mechanics understanding.
Question #2
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Which scientific instrument is explicitly designed for measuring extremely small lengths with high precision by using a main scale and a rotating circular scale?
Correct Answer: Option B
Explanation:
A micrometer screw gauge uses the principle of a screw rotating in a nut to measure very tiny dimensions (like the diameter of a thin wire). It features a linear main scale and a rotating circular scale on the thimble. While a Vernier caliper measures small distances using sliding scales, the screw gauge generally offers greater precision (least count often 0.01 mm or 0.001 mm).
A micrometer screw gauge uses the principle of a screw rotating in a nut to measure very tiny dimensions (like the diameter of a thin wire). It features a linear main scale and a rotating circular scale on the thimble. While a Vernier caliper measures small distances using sliding scales, the screw gauge generally offers greater precision (least count often 0.01 mm or 0.001 mm).
Question #3
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The gravitational potential strictly at the center of a solid, uniform Earth of mass M and radius R is:
Correct Answer: Option C
Explanation:
The gravitational potential V inside a uniform solid sphere at a distance r from the center is V = -GM * (3R^2 - r^2) / (2R^3). At the exact center of the Earth, r = 0. Substituting r = 0 gives V = -GM(3R^2) / 2R^3 = -3GM / 2R. The potential is strictly non-zero and highly negative.
The gravitational potential V inside a uniform solid sphere at a distance r from the center is V = -GM * (3R^2 - r^2) / (2R^3). At the exact center of the Earth, r = 0. Substituting r = 0 gives V = -GM(3R^2) / 2R^3 = -3GM / 2R. The potential is strictly non-zero and highly negative.
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