1
JEE Main 2017 (Online) 8th April Morning Slot
+4
-1
A compressive force, F is applied at the two ends of a long thin steel rod. It is heated, simultaneously, such that its temperature increases by $$\Delta$$T. The net change in its length is zero. Let $$\ell$$ be the length of the rod, A its area of cross-section,Y its Young’s modulus, and $$\alpha$$ its coefficient of linear expansion. Then, F is equal to :
A
$$\ell$$2 Y$$\alpha$$ $$\Delta$$T
B
$$\ell$$A Y$$\alpha$$ $$\Delta$$T
C
A Y$$\alpha$$ $$\Delta$$T
D
$${{AY} \over {\alpha \,\Delta T}}$$
2
JEE Main 2017 (Online) 8th April Morning Slot
+4
-1
Out of Syllabus
An engine operates by taking n moles of an ideal gas through the cycle ABCDA shown in figure. The thermal efficiency of the engine is : (Take Cv = 1.5 R, where R is gas constant)

A
0.24
B
0.15
C
0.32
D
0.08
3
JEE Main 2017 (Online) 8th April Morning Slot
+4
-1
An ideal gas has molecules with 5 degrees of freedom. The ratio of specific heats at constant pressure (Cp ) and at constant volume (Cv) is :
A
6
B
$${7 \over 2}$$
C
$${5 \over 2}$$
D
$${7 \over 5}$$
4
JEE Main 2017 (Offline)
+4
-1
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 75oC. T is given by: (Given : room temperature = 30oC, specific heat of copper = 0.1 cal/gmoC)
A
825oC
B
800oC
C
885oC
D
1250oC
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