Q.

Two strings (A, B) having linear densities μA=2×10-4 kg/m and μB=4×10-4 kg/m and lengths LA=2.5 m and LB=1.5 m respectively are joined. Free ends of A and B are tied to two rigid supports C and D, respectively creating a tension of 500 N in the wire. Two identical pulses, sent from C and D ends, take time t1 and t2 respectively to reach the joint. The ratio t1/t2 is   [2026]

1 1.18  
2 1.90  
3 1.08  
4 1.67  

Ans.

(1)

Given  LA=2.5 m,  LB=1.5 m,  T=500 N

vA=TμA=5002×10-4=510×102 m/s

vB=TμB=5004×10-4=55×102 m/s

t1=LAvA=2.5510×10-2 s

t2=LBvB=1.555×10-2 s

  t1t2=2.5510×551.5=53×12=1.661.41=1.18