The part of the eye that controls the amount of light entering is MCQ with Answer and Explanation

Explanation:
KE ∝ p². Double KE ⇒ p_new = √2 p_old ⇒ increase = (√2 - 1)×100% ≈ 41.4%. Memory tip: 'KE ∝ p²; %Δp ≈ ½ %ΔKE for small changes, but use exact for large'. Energy-momentum relation frequently tested in competitive exams.

Explanation:
KE = ½mv², ΔKE/KE = Δm/m + 2 Δv/v = 1% + 4% = 5%.

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).