The slope of a distance-time graph for a body at rest is MCQ with Answer and Explanation

Explanation:
K.E. = ½ m v² = ½ × 2 × 5² = 1 × 25 = 25 J. Use formula correctly. If velocity doubled, KE quadrupled. Unit joule.

Explanation:
Coefficient of performance (COP) for refrigerator: COP = Q₂ / W, where Q₂ is heat extracted from cold reservoir, W is work input. By energy conservation, Q₁ = Q₂ + W (heat rejected to hot reservoir). COP > 1 typically. Option A is inverse; C and D relate to heat engine efficiency. Memory aid: 'Refrigerator COP = desired output (cooling) / work input'. This thermodynamics definition is frequently tested in competitive exams. Always distinguish refrigerator COP (cooling effect per work) from heat engine efficiency (work output per heat input).

Explanation:
ΔPE = mgΔh = 4×10×(8-2) = 4×10×6 = 240 J.