Properties of Solids & Fluids · JEE Main previous year questions

2018 3 questions

1. Q382018 · 16 Apr 2018 · Shift 1

   A small soap bubble of radius 4 cm is trapped inside another bubble of radius 6 cm without any contact. Let ${\text{P}}_2$ be the pressure inside the inner bubble and ${\text{P}}_0$, the pressure outside the outer bubble. Radius of another bubble with pressure difference ${\text{P}}_2-{\text{P}}_0$ between its inside and outside would be :

   1. A.12 cm
   2. B.2.4 cm
   3. C.6 cm
   4. D.4.8 cm
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   Answer: B

2. Q392018 · 8 Apr 2018 · Shift 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, $\left(\frac{dr}{r}\right)$ is:

   1. A.$\frac{mg}{Ka}$
   2. B.$\frac{Ka}{mg}$
   3. C.$\frac{Ka}{3mg}$
   4. D.$\frac{mg}{3Ka}$
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   Answer: D

3. Q412018 · 8 Apr 2018 · Shift 1

   The mass of a hydrogen molecule is $3.32\times 10^{-27}\mathrm{kg}$. If $10^{23}$ hydrogen molecules strike, per second, a fixed wall of area $2\mathrm{c}{\mathrm{m}}^2$ at an angle of $45^{\circ }$ to the normal, and rebound elastically with a speed of $10^{3}m/s$, then the pressure on the wall is nearly:

   1. A.$2.35\times 10^3\mathrm{N}{\mathrm{m}}^{-2}$
   2. B.$4.70\times 10^3\mathrm{N}{\mathrm{m}}^{-2}$
   3. C.$2.35\times 10^2\mathrm{N}{\mathrm{m}}^{-2}$
   4. D.$4.70\times 10^2\mathrm{N}{\mathrm{m}}^{-2}$
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   Answer: A