JEE PHYSICS MCQ: MECHANICAL PROPERTIES OF FLUIDS

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The length of a needle floating on water is

2.5 \mathrm{~cm}

. How much minimum force, in addition to the weight of the needle, will be needed to lift the needle above the surface of water? Surface tension of water

=7.2 \times 10^{-4} \mathrm{~Ncm}^{-1}

View answer and explanation

Correct option: A

3.6 \times 10^{-3} \mathrm{~N}

The correct answer is A (

3.6 \times 10^{-3} \mathrm{~N}

) because the force needed to lift the needle is calculated using the surface tension and the length of contact.

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The average mass that must be lifted by a hydraulic press is

80 \mathrm{~kg}

. If the radius of the larger piston is five times that of the smaller piston, what is the minimum force that must be applied? A small drop of oil spreads over water because A film of water is formed between two straight parallel wires of length

20 \mathrm{~cm}

with separation of

0.5 \mathrm{~cm}

. The work done to increase the separation by

0.1 \mathrm{~cm}

is: The velocity of water in a river is

15 \mathrm{~m} / \mathrm{s}

near the surface. If the river is

5 \mathrm{~m}

deep, find the shearing stress between the horizontal layers of water. The coefficient of viscosity of water

=10^{-2}

poise. A liquid rises to a height of 2 cm in a capillary tube. The angle of contact between the solid and the liquid is zero. The tube is depressed more so that the top of capillary tube is only one cm above the liquid. Then the apparent angle of contact between the solid and liquid is An object weights

m_1

in a liquid of density

d_1

and that in liquid of density

d_2

m_2

. The density of th object is