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EEJ MAIN Physics QUESTION #7106
Question 1
A wire has length $l_1$ at tension $T_1$ and $l_2$ at tension $T_2$. What is its natural length? [cite: 506, 507]
  • $\frac{T_1l_1 - T_2l_2}{T_2 - T_1}$
  • $\frac{l_1 + l_2}{2}$
  • $\frac{T_2l_1 + T_1l_2}{T_2 + T_1}$
  • $\frac{T_2l_1 - T_1l_2}{T_2 - T_1}$✔️
Correct Answer Explanation

Using $l = L + \frac{TL}{AY} = L + kT$:

  • $l_1 = L + kT_1$ and $l_2 = L + kT_2$ [cite: 506]
  • Solving for $L$ by eliminating $k$: $L = \frac{T_2l_1 - T_1l_2}{T_2 - T_1}$[cite: 515].