NDA2026General AbilityGeneral ScienceActual
A pendulum of length L oscillates with an angular amplitude of = 60^ and time period T . Let T₀ = 2 L g be the time period for small angle of oscillations, where g is the acceleration due to gravity. If air resistance is negligibly small and the string remains straight, then which one of the following is correct?
Options
- AT will be slightly greater than T₀ .
- BT will be slightly smaller than T₀ .
- CT will be exactly equal to T₀ .
- DT will depend upon the mass of the bob.
Correct answer
A. T will be slightly greater than T₀ .
Step-by-step solution
The restoring torque acting on the pendulum is = -mgL . The angular acceleration is = - g L . For small angular amplitudes, , which gives the time period T₀ = 2 L g . For a large angular amplitude ( = 60^ ), Due to the smaller restoring torque, the angular acceleration is reduced, which increases the time taken to complete an oscillation. The exact time period for large amplitudes is given by the series expansion T = T₀ ( 1 + 1 4 ^2 ( ₀ 2 ) + ) . Since ₀ = 60^ , the terms in the bracket are positive, yielding T > T