1
JEE Main 2019 (Online) 9th January Morning Slot
+4
-1
A rod, of length L at room temperature and uniform area of cross section A, is made of a metal having coefficient of linear expansion $$\alpha$$/oC. It is observed that an external compressive force F, is applied on each of its ends, prevents any change in the length of the rod, when its temperature rises by $$\Delta$$TK. Young's modulus, Y, for this metal is :
A
$${F \over {A\alpha \Delta T}}$$
B
$${F \over {A\alpha (\Delta T - 273)}}$$
C
$${F \over {2A\alpha \Delta T}}$$
D
$${{2F} \over {A\alpha \Delta T}}$$
2
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
A small soap bubble of radius 4 cm is trapped inside another bubble of radius 6 cm without any contact. Let P2 be the pressure inside the inner bubble and P0, the pressure outside the outer bubble. Radius of another bubble with pressure difference P2 $$-$$ P0 between its inside and outside would be :
A
12 cm
B
2.4 cm
C
6 cm
D
4.8 cm
3
JEE Main 2018 (Offline)
+4
-1
A solid sphere of radius r made of a soft material of bulk modulus K is surrounded by a liquid in a cylindrical container. A massless piston of area a floats on the surface of the liquid, covering entire cross section of cylindrical container. When a mass m is placed on the surface of the piston to compress the liquid, the fractional decrement in the radius of the sphere, $$\left( {{dr \over r}} \right)$$ is:
A
$${{mg} \over {Ka}}$$
B
$${{Ka} \over {mg}}$$
C
$${{Ka} \over {3mg}}$$
D
$${{mg} \over {3Ka}}$$
4
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
When an air bubble of radius r rises from the bottom to the surface of a lake its radius becomes $${{5r} \over 4}.$$ Taking the atmospheric pressure to be equal to 10 m height of water column, the depth of the lake would approximately be (ignore the surface tension and the effect of temperature) :
A
11.2 m
B
8.7 m
C
9.5 m
D
10.5 m
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