Question

A man generates a symmetrical pulse in a strong by moving his hand up and down. At t = 0 the point in his hand moves downward. The pulse travels with speed of 3m?s on the string & his hands passes 6 times in each second from the mean position. Then the point on the string at a distance 3m will reach its upper extreme first time at time t =

Answer 1

If hand passes 6 times from mean position in one second, then we know string creates 3 wavelengths or 3 cycles in one second, which means frequency is 3 Hz

λ = V/f

= (3m/s)/3 = 1 m

If λ = 1m, the point which have 3m distance is located at no.(6) (in the diagram).

to reach its upper extreme ----> have to travel 3λ/4 distance

time to travel 3λ = 1 second

time to travel λ = 1/3 seconds

time to travel 3λ/4 = (1/3) * (3/4) seconds

= 1/4 seconds = 0.25 seconds

Answer :0.25 seconds