MCQ practice · SSC Physics Board questions · Chapter 7: Waves and Sound
Which of the following relations is correct?
Think it through first, then pick an option.
- a g = 4π² T²/L
- b L = 4π g/T²
- c T = 2π √(g/L)
- d g = 4π² L/T²
Answer and explanation
Correct answer: d g = 4π² L/T²
Squaring both sides of T = 2π√(l/g) and solving for g gives g = 4π²l/T²; this is how g is found from a measured time period.
Why the other options are wrong
- a g = 4π² T²/L: From T = 2π√(l/g) we get g = 4π²l/T²; here the places of T² and l are swapped.
- b L = 4π g/T²: The formula gives L = gT²/(4π²); here 4π is not squared and g and T² are in the wrong places.
- c T = 2π √(g/L): The book's formula is T = 2π√(l/g); here g and L have swapped places.
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