1
WB JEE 2021
+2
-0.5 Under isothermal conditions, two soap bubbles of radii a and b coalesce to form a single bubble of radius c. If the external pressure is p, then surface tension of the bubbles is
A
$${{p({c^3} - {a^3} + {b^3})} \over {4({a^2} + {b^2} - {c^2})}}$$
B
$${{p({c^3} - {a^3} - {b^3})} \over {4({a^2} + {b^2} - {c^2})}}$$
C
$${{p({c^2} + {a^3} - {b^2})} \over {4({a^3} + {b^3} - {c^3})}}$$
D
$${{p({a^3} + {b^3} - {c^3})} \over {4({a^2} + {b^2} - {c^2})}}$$
2
WB JEE 2020
+1
-0.25 A steel and a brass wire, each of length 50 cm and cross-sectional area 0.005 cm2 hang from a ceiling and are 15 cm apart. Lower ends of the wires are attached to a light horizontal bar. A suitable downward load is applied to the bar, so that each of the wires extends in length by 0.1 cm. At what distance from the steel wire, the load must be applied?

[Young's modulus of steel = 2 $$\times$$ 1012 dyne/cm2 and that of brass = 1 $$\times$$ 1012 dyne/cm2]
A
7.5 cm
B
5 cm
C
10 cm
D
3 cm
3
WB JEE 2020
+1
-0.25 Which of the following diagrams correctly shows the relation between the terminal velocity vT of a spherical body falling in a liquid and viscosity $$\eta$$ of the liquid?
A B C D 4
WB JEE 2019
+1
-0.25 A compressive force is applied to a uniform rod of rectangular cross-section so that its length decreases by 1%. If the Poisson's ratio for the material of the rod be 0.2, which of the following statements is correct?

"The volume approximately ................."
A
decreases by 1%
B
decreases by 0.8%
C
decreases by 0.6%
D
increases by 0.2%
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Physics
Mechanics
Electricity
Optics
Modern Physics
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Organic Chemistry
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