A car travels first half distance at 40 km/h and second half at 60 km/h. Average speed is
A. 45 km/h
B. 48 km/h
C. 52 km/h
D. 50 km/h
Answer: Option B
Solution (By JKExamLibrary)
Average speed = 2v₁v₂/(v₁+v₂) = 2×40×60/(40+60) = 4800/100 = 48 km/h. Not arithmetic mean (50). For equal distances, harmonic mean of speeds. If times equal, arithmetic mean applies.
Explanation:
Planck's constant h = E/ν. Dimensions: [ML²T⁻²]/[T⁻¹] = [ML²T⁻¹]. Angular momentum = mvr = [ML²T⁻¹]. Linear momentum [MLT⁻¹], force [MLT⁻²], energy [ML²T⁻²]. So angular momentum matches. This is a frequently asked SSC question.
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