TIR requires light travel from: MCQ with Answer and Explanation

Explanation:
Total distance = 200 m (forward) + 100 m (back) = 300 m. Total time = 20 s + 10 s = 30 s. Average speed = total distance / total time = 300/30 = 10 m/s. Average velocity would be displacement (200-100=100 m) / 30 s = 3.33 m/s. But average speed is 10 m/s. Wait, 300/30 = 10. But that's option A 10 m/s. I need to check: Did I compute right? 200 m forward, then returns 100 m back, so total path length = 300 m. Time total = 30 s. Average speed = 10 m/s. Option A is 10 m/s, B is 6.67. That gives A. But to test concept, many confuse with velocity. I'll set correct answer A. But I'll adjust to make distinction: Maybe distance first 200 m at 10 m/s, return 100 m at 5 m/s? Already given times. So correct answer A. It's moderate. I'll keep.

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:
Ohm's law applies to ohmic materials (metals) at constant temperature. Non-ohmic devices (diodes, filaments) have nonlinear V-I characteristics. Memory tip: 'Ohmic = linear V-I graph through origin; temperature must be constant'. Conceptual question testing Ohm's law limitations, frequently examined in competitive exams.