A 100 W bulb is used for 10 hours. Energy consumed is MCQ with Answer and Explanation

Explanation:
Speed of sound: solids > liquids > gases. In steel ~5000 m/s, water ~1500 m/s, air ~340 m/s. Vacuum no propagation. Speed depends on density and elasticity.

Explanation:
Mass m = 20 g = 0.02 kg. Momentum p = m v = 0.02 × 200 = 4 kg m/s. Always convert mass to kg. Momentum unit kg·m/s.

Explanation:
Energy stored in capacitor U = ½CV² = ½QV = Q²/(2C). This derives from work done to charge the capacitor against increasing voltage. Option A has wrong dimensions (energy should be joules, CV is coulomb-volt = joule, but missing factor ½); C and D are dimensionally incorrect. Memory tip: 'Capacitor energy = ½CV², analogous to spring energy ½kx²'. This formula-based question tests electrostatics knowledge, frequently appearing in competitive exams. Always recall the three equivalent forms and choose based on given quantities.