A body of mass m is taken from Earth's surface to a height equal to twice Earth's radius. Change in potential energy is MCQ with Answer and Explanation

Explanation:
Conservation of linear momentum follows from Newton's third law (action-reaction pairs) and second law. For an isolated system, internal forces cancel in pairs (third law), so net force = 0, thus dp/dt = 0 (second law), meaning momentum constant. While derivable from second law with third law, the direct foundational link is third law. Memory aid: 'Momentum conservation ⇔ no external force ⇔ internal forces cancel (third law)'. This conceptual question tests mechanics fundamentals, crucial for competitive exams. Always distinguish conservation laws: momentum (from spatial symmetry), energy (from time symmetry).

Explanation:
Newton's second law: F = ma ⇒ a = F/m = 20 N / 5 kg = 4 m/s². Direct application of fundamental dynamics equation. Memory tip: Always convert to SI units first; here already in kg and N. Basic numerical testing F=ma application, commonly appearing in competitive exams to verify formula recall and unit handling.

Explanation:
Water's high specific heat (4186 J/kg·K) means it absorbs/releases large heat with small temperature change. This stabilizes temperatures: in engines, water coolant absorbs heat without large ΔT; in organisms, it buffers against temperature fluctuations. Memory tip: 'High specific heat = thermal buffer; water moderates climate and body temperature'. This application question tests understanding of material properties, frequently appearing in competitive exams. Always link physical properties to real-world uses; competitive exams emphasize practical implications of physics concepts.