The amplitude of a simple pendulum is 10 cm. When the pendulum is at a displacement of 4 cm from the mean position, the ratio of kinetic and potential energies at that point is

Options

A. 5.25
B. 2.5
C. 4.5
D. 7.5

Answer

A

Explanation

`(K. E)/( P. E) = ((1)/(2) m omega ^(2) (A ^(2) - x ^(2)))/( (1)/(2) m omega ^(2) x ^(2))`
`(K. E)/( P.E) = (A ^(2) - x ^(2))/( x ^(2))`
Given A = 10 cm and x = 4 cm
`(KE)/( PE) = (10 ^(2) - 4 ^(2))/( 4 ^(2)) = ( 84)/(16) = (21)/(4) = 5.25`