If a force of 10 N acts on a body and displaces it by 2 m in the direction of the force, the work done is:
A. 12 J
B. 20 J
C. 5 J
D. 0 J
Answer: Option B
Solution (By JKSSB Mock Tests)
Work done (W) is calculated as the dot product of force and displacement: W = F × d × cos(θ). Since the displacement is in the direction of the force, the angle θ is 0°, and cos(0°) = 1. W = 10 N × 2 m × 1 = 20 Joules (J).
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.
Explanation:
Sir C. V. Raman was awarded the Nobel Prize in Physics in 1930 for discovering the 'Raman Effect'. The Raman effect involves the inelastic scattering of photons by molecules, resulting in a change in wavelength. This discovery proved that light has particle-like characteristics. National Science Day in India (Feb 28) commemorates this discovery.
Explanation:
When equal distances are covered with different speeds v1 and v2, the average speed is not the arithmetic mean, but the harmonic mean of the two speeds. Total distance = 2x. Total time = (x/v1) + (x/v2). Average speed = Total Distance / Total Time = 2x / [x(1/v1 + 1/v2)] = 2v1v2 / (v1 + v2).
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