JEE MAIN - Physics (2019 - 12th April Morning Slot - No. 6)
At 40o C, a brass wire of 1 mm radius is hung from the ceiling. A small mass, M is hung from the free end of
the wire. When the wire is cooled down from 40oC to 20oC it regains its original length of 0.2 m. The value
of M is close to :
(Coefficient of linear expansion and Young’s modulus of brass are 10–5
/oC and 1011 N/m
2
, respectively; g=
10 ms–2
)
1.5 kg
0.5 kg
9 kg
0.9 kg
Explanation
$$Mg = \left( {{{Ay} \over \ell }} \right)\Delta \ell $$
$$Mg = \left( {Ay} \right)\alpha \Delta T = 2\pi $$
It is closest to 9
$$Mg = \left( {Ay} \right)\alpha \Delta T = 2\pi $$
It is closest to 9
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