A satellite moves in a circular orbit around the Earth at a constant speed. The work done by the gravitational force on the satellite is: MCQ with Answer and Explanation
A satellite moves in a circular orbit around the Earth at a constant speed. The work done by the gravitational force on the satellite is:
A. Maximum
B. Negative
C. Positive
D. Zero
Answer: Option D
Solution (By JKSSB Mock Tests)
Work is defined as W = F.d.cos(θ). For a satellite in a circular orbit, the gravitational force acts as the centripetal force, directing entirely towards the center of the Earth. The displacement of the satellite at any instant is tangential. Since the angle between force and displacement is exactly 90°, cos(90°) = 0, meaning zero work is done.
Explanation:
Lactometer is a specialized hydrometer for measuring milk purity/density. It works on Archimedes' principle: pure milk has specific density; adulteration (with water) changes density, altering lactometer reading. While it measures density, its specific application is milk testing. Option B is partially correct but not specific; competitive exams expect the precise application. Memory tip: 'Lacto = milk; meter = measure'. This application-based question tests knowledge of scientific instruments in daily life, frequently appearing in competitive exams. Always note context-specific uses of general instruments.
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