Power P = V²/R => R = V²/P = 200²/100 = 40000/100 = 400 Ω. Also current I = P/V = 0.5 A, R = V/I = 200/0.5 = 400 Ω. Use P = V²/R for direct calculation.
A ball is dropped from a height 'h' and simultaneously another ball is thrown horizontally from the same height. Which ball will hit the ground first? (Neglect air resistance)
Explanation:
Vertical and horizontal motions are completely independent. Both balls have zero initial downward (vertical) velocity and both are subject to the same downward acceleration due to gravity (g). Since the vertical height (h) is the same, using h = ut + ½gt², time t = √(2h/g) applies equally to both. Thus, they hit the ground simultaneously.
Explanation:
Water has exceptionally high specific heat (4200 J/kg°C) due to hydrogen bonding. Used as coolant. Iron ~450, copper ~385, aluminium ~900. High specific heat moderates climate.
Explanation:
Heat for phase change Q = m·L_f, where L_f is latent heat of fusion. Thus Q = 2 kg × 336 kJ/kg = 672 kJ. This direct application tests calorimetry fundamentals. Memory aid: 'Latent heat: Q = mL; no temperature change during phase transition'. Competitive exams frequently test such calculations with standard values. Always ensure units match (kg and kJ/kg here); convert if necessary. This problem assesses basic formula application skills essential for thermodynamics sections.
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