JEE Main · 2017 · 02 Apr 2017 · Offline · Heat & Thermodynamics

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A copper ball of mass 100 gm is at a temperature T. It is dropped in a copper calorimeter of mass 100 gm, filled with 170 gm of water at room temperature. Subsequently, the temperature of the system is found to be

7 5^{\circ} C

. T is given by: (Given: room temperature

= 3 0^{\circ} C

, specific heat of copper

= 0.1

cal/gm

^{\circ} C

)

(A) $125 0^{\circ} C$
(B) $82 5^{\circ} C$
(C) $80 0^{\circ} C$
(D) $88 5^{\circ} C$ ✓ Correct

Answer: (D)

Solution

Heat lost by the hot ball equals heat gained by the water and the calorimeter:

100 (0.1) (T - 75) = 170 (1) (75 - 30) + 100 (0.1) (75 - 30)

. The right side is

7650 + 450 = 8100

, so

10 (T - 75) = 8100

, giving

T - 75 = 810

and

T = 88 5^{\circ}

JEE Main · 2017 · 02 Apr 2017 · Offline · Single correct option

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