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Three equal masses 3 kg are connected by...

Three equal masses 3 kg are connected by massless string of cross sectional area `0.005 cm^(-2)` and Young's modulus `2xx 10^(11) N//m^(-2)`. In the absence of friction the longitudes strain in the wire

A

A is `10^(-4)`

B

B is `2 xx 10^(-4)`

C

Both (a) and (b)

D

None the these

Text Solution

Verified by Experts

The correct Answer is:
C
`3g - T_(B) = 3a`
`T_(A) = 3a`
`T_(B) - T_(A) = 3a` are the equations defining the motion

Sloving we get, `a = (3g)/(9) = (g)/(3), T_(A) = g and T_(B) = 2g`
So, Strain in `A = (T_(A))/(aY) = (g)/(0.005 xx 10^(-4) xx Y) = 10^(-4)`
Strain in `B = (T_(B))/(ay) = (2g)/(0.005 xx Yxx 10^(-4))= 2xx 10^(-4)`
So, choice (a) and (b) are correct and so choice (c) is correct answer.
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