A man generates a symmetrical pulse in a string by moving his hand up

1.	A man generates a symmetrical pulse in a string by moving his hand up and down. At t=0, the point in his hand moves downwards from mean position. The pulse travels with speed 3 m/s on the string and his hand passes 6 times in each second from the mean position. Then the point of the string at a distance 3 m will reach its upper extreme first time at t=
Answer» Firstly, we have to draw the pulse wave (see ATTACHED diagram). If HAND passes 6 times from the mean position in one second, then we know that string CREATES 3 wave lengths (λ) or 3 cycles after 1 second. That means frequency (F) of the wave is 3 Hz. Now we can use below equation to calculate the value of wave length. V = fλ (V = velocity of the wave) 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

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

Answer»

Firstly, we have to draw the pulse wave (see ATTACHED diagram).

If HAND passes 6 times from the mean position in one second, then we know that string CREATES 3 wave lengths (λ) or 3 cycles after 1 second.

That means frequency (F) of the wave is 3 Hz.

Now we can use below equation to calculate the value of wave length.

V = fλ (V = velocity of the wave)

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