JEE Previous Year Question
The length of a light string is 1.4 m when the tension on it is 5 N. If the tension increases to 7 N, the length of the string is 1.56 m. The original length of the string is m.
Topic: JEE PYQ
Answer: 1. Full step-by-step solution below.
Correct answer: 1
Solution
(1)To find the original length of the string, we use the relationship between tension, elasticity constant , and the change in length of the string.
Given the equation for tension:
where is the length of the string under tension and is the original length.
When the tension is 5 N, the equation becomes:
When the tension increases to 7 N, the equation is:
By setting up a ratio from the two equations, we have:
Solving this proportion gives us the original
length :
Thus, the original length of the string is 1 meter.
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