Two long strings A and B, each having linear mass density `1.2 xx 10 ^-2 kg m^-1`, are stretched by different tensions 4.8 N and 7.5 N respectively and are kept parallel to each other with their left ends at x = 0. Wave pulses are produced on the strings at the left ends at t = 0 on string A and at t = 20 ms on string B. When and where will the pulse on B overtake that on A ?

Answer

A, B

Explanation

`m=1.2xx10^-2kg/m, T=4.8N`
`rarr Va=sqrt((4.8)/((1/2xx10^-2)))=20m/s`
`m=1.2xx10^-2kg/m`
`Tb=7.5/((1.5xx10^-2))=25m/s`
`t_1=0 in string A `
`t_1` =0+20 ms`
`=20xx10^-3=0.02sec`
In 0.02 sec A has travelled
`=20xx0.02=0.4m`
Relative speed between A and B
`=2-20=5m/s`
Time taken for B to overtake A`
`=s/v=0.4/5=0.08 sec.