1
JEE Main 2021 (Online) 31st August Morning Shift
+4
-1
A uniform heavy rod of weight 10 kg ms$$-$$2, cross-sectional area 100 cm2 and length 20 cm is hanging from a fixed support. Young modulus of the material of the rod is 2 $$\times$$ 1011 Nm$$-$$2. Neglecting the lateral contraction, find the elongation of rod due to its own weight.
A
2 $$\times$$ 10$$-$$9 m
B
5 $$\times$$ 10$$-$$8 m
C
4 $$\times$$ 10$$-$$8 m
D
5 $$\times$$ 10$$-$$10 m
2
JEE Main 2021 (Online) 27th August Morning Shift
+4
-1
In Millikan's oil drop experiment, what is viscous force acting on an uncharged drop of radius 2.0 $$\times$$ 10$$-$$5 m and density 1.2 $$\times$$ 103 kgm$$-$$3 ? Take viscosity of liquid = 1.8 $$\times$$ 10$$-$$5 Nsm$$-$$2. (Neglect buoyancy due to air).
A
3.8 $$\times$$ 10$$-$$11 N
B
3.9 $$\times$$ 10$$-$$10 N
C
1.8 $$\times$$ 10$$-$$10 N
D
5.8 $$\times$$ 10$$-$$10 N
3
JEE Main 2021 (Online) 26th August Evening Shift
+4
-1
Two blocks of masses 3 kg and 5 kg are connected by a metal wire going over a smooth pulley. The breaking stress of the metal is $${{24} \over \pi } \times {10^2}$$ Nm-2. What is the minimum radius of the wire ? (Take g = 10 ms-2)

A
125 cm
B
1250 cm
C
12.5 cm
D
1.25 cm
4
JEE Main 2021 (Online) 26th August Morning Shift
+4
-1
Two narrow bores of diameter 5.0 mm and 8.0 mm are joined together to form a U-shaped tube open at both ends. If this U-tube contains water, what is the difference in the level of two limbs of the tube. [Take surface tension of water T = 7.3 $$\times$$ 10$$-$$2 Nm$$-$$1, angle of contact = 0, g = 10 ms2 and density of water = 1.0 $$\times$$ 103 kg m$$-$$3]
A
3.62 mm
B
2.19 mm
C
5.34 mm
D
4.97 mm
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