21) The velocity - time diagram of a harmonic oscillator is shown in the adjoining figure. The frequency of oscillation is.
(i) 25 Hz
(ii) 50 Hz
(iii) 12.25 Hz
(iv) 33.3 Hz

Dear Student ,
to complete one oscillation it takes 0.04 s.
So the time period of oscillation is , T = 0.04 s
So the frequency of the oscillation is , n = 1/T = 1/ 0.04 = 25 Hz

Regards