The work done by the gravitational force when a body is moved horizontally on Earth's surface is:
A. Positive
B. Negative
C. Zero
D. Depends on speed
Answer: Option C
Solution (By JKSSB Mock Tests)
Gravitational force acts vertically downward. For horizontal displacement, the angle between force and displacement is 90°, so work W = F·d·cos90° = 0. Gravity does no work for horizontal motion; it only does work for vertical displacement components. Memory aid: 'Work = F d cosθ; θ=90° ⇒ W=0'.
Explanation:
Isaac Newton formulated the universal law of gravitation in his Principia Mathematica (1687), stating F = Gm₁m₂/r². Galileo studied falling bodies; Kepler derived planetary motion laws; Einstein developed general relativity (gravity as spacetime curvature). Memory aid: 'Newton = gravity apple story'. This history-based question tests knowledge of key scientific contributions, frequently appearing in competitive exams. Always associate scientists with their specific discoveries to avoid confusion between classical and modern physics pioneers.
Explanation:
Photovoltaic cell (solar cell) directly converts sunlight to electricity. Solar heater uses sun to heat water, not electricity. Wind turbine converts wind energy. Battery stores chemical energy.
Explanation:
Displacement has both magnitude and direction, vector. Distance is scalar (path length). Speed scalar. Energy scalar. Vector examples: velocity, force, acceleration.
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