An iron sphere of mass 10 kg has same diameter as an aluminium sphere of mass 3.5 kg. Both fall from rest in vacuum. Which hits ground first? MCQ with Answer and Explanation

Explanation:
a ∝ -x; magnitude maximum when |x| maximum (extremes). At mean position x=0 ⇒ a=0. Velocity maximum at mean position. Memory aid: 'SHM: a max at extremes, v max at center'. Oscillation concept frequently tested in competitive exams to verify SHM characteristics understanding.

Explanation:
Position-time graph as parabola: x = x₀ + ut + ½at². This quadratic form indicates constant acceleration 'a'. If acceleration were changing, the graph would be cubic or higher order. Constant velocity would produce a straight line (linear graph). Upward opening parabola implies positive acceleration. Graph interpretation skill is essential: slope of x-t graph = velocity; curvature indicates acceleration. Memory tip: Parabolic x-t graph ⇔ constant acceleration; linear x-t graph ⇔ constant velocity. Competitive exams frequently test graph-concept correlations.

Explanation:
V_s/V_p = N_s/N_p ⇒ V_s = 100×(5/1) = 500V. Step-up transformer increases voltage. Memory aid: 'Turns ratio = voltage ratio; current ratio inverse'. Direct transformer formula application frequently tested in competitive exams with ratio calculations.