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JEE Physics Solved Question Paper 2018

Multiple Choice Questions

Two masses m₁ = 5 kg and m₂ = 10 kg, connected by an inextensible string over a frictionless pulley, are moving as shown in the figure. The coefficient of friction of the horizontal surface is 0.15. The minimum weight m that should be put on top of m₂ to stop the motion is :

10.3 kg
18.3 kg
27.3 kg
43.3 kg

In a collinear collision, a particle with an initial speed v0 strikes a stationary particle of the same mass. If the final total kinetic energy is 50% greater than the original kinetic energy, the magnitude of the relative velocity between the two particles, after the collision, is:

v_o/4
v₀/2

A particle is moving with a uniform speed in a circular orbit of radius R in a central force inversely proportional to the n^th power of R. If the period of rotation of the particle is T, then:

$T \propto R^{n / 2}$
$T \propto R^{3 / 2} f o r a n y n$
$T \propto R^{\frac{n}{2} + 1}$
$T \propto R^{\frac{n + 1}{2}}$

It is found that if a neutron suffers an elastic collinear collision with deuterium at rest, fractional loss of its energy is p_d; while for its similar collision with carbon nucleus at rest, fractional loss of energy is p_c. The values of p_d and p_c are respectively :

(0,1)
(.89,.28)
(.28,.89)
(0,0)

All the graphs below are intended to represent the same motion. One of them does it incorrectly. Pick it up.

A silver atom in a solid oscillates in simple harmonic motion in some direction with a frequency of 10¹²/sec. What is the force constant of the bonds connecting one atom with the other? (Mole wt. of silver = 108 and Avagadro number = 6.02 × 10²³ gm mole^–1)

5.5 N/m
6.4 N/m
7.1 N/m
2.2 N/m

A granite rod of 60 cm length is clamped at its middle point and is set into longitudinal vibrations. The density of granite is 2.7 x 10³ kg/m³and its Young’s modulus is 9.27 x 10¹⁰ Pa. What will be the fundamental frequency of the longitudinal vibrations?

7.5 kHz
5 kHz
2.5 kHz
10 kHz

The density of a material in the shape of a cube is determined by measuring three sides of the cube and its mass. If the relative errors in measuring the mass and length are respectively 1.5% and 1%, the maximum error in determining the density is:

6%
2.5%
3.5%
4.5%

9.
Two moles of an ideal monoatomic gas occupies a volume V at 27°C. The gas expands adiabatically to a volume 2 V. Calculate (a) the final temperature of the gas and (b) change in its internal energy.

(a) 195 K (b) 2.7 kJ

(a) 189 K (b) 2.7 kJ

(a) 195 K (b) –2.7 kJ

(a) 189 K (b) – 2.7 kJ

(a) 189 K (b) – 2.7 kJ

In an adiabatic Process

$T V^{γ - 1} = C o n s \tan t O r T_{1} {V_{1}}^{γ - 1} = T_{2} {V_{2}}^{γ - 1} F o r m o n o a t o m i c g a s γ = \frac{5}{3} (300) V^{2 / 3} = T_{2} (2 V)^{2 / 3} \Rightarrow T_{2} = \frac{300}{(2)^{2 / 3}} T_{2} = 189 K (f i n a l t e m p e r a t u r e) C h a n g e i n i n t e r n a l e n e r g y, ∆ U = n \frac{f}{2} R ∆ T = 2 (\frac{3}{2}) (\frac{25}{3}) (- 111) = - 2.7 k J$

10.

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 the area a floats on the surface of the liquid, covering an 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, (dr/r), is