Other Physics · JEE Main previous year questions

2018 11 questions

1. Q322018 · 16 Apr 2018 · Shift 1

   Let $\vec{A}=\left(\hat{i}+\hat{j}\right)$ and, $\vec{B}=\left(2\hat{i}-\hat{j}\right)$. The magnitude of a coplanar vector $\vec{C}$ such that $\vec{A}\cdot \vec{C}=\vec{B}\cdot \vec{C}=\vec{A}\cdot \vec{B}$, is given by :

   1. A.$\sqrt{\frac{10}{9}}$
   2. B.$\sqrt{\frac{5}{9}}$
   3. C.$\sqrt{\frac{20}{9}}$
   4. D.$\sqrt{\frac{9}{12}}$
   Show answer

   Answer: B

2. Q342018 · 16 Apr 2018 · Shift 1

   Two particles of the same mass m are moving in circular orbits because of force, given by $F(r)=\frac{-16}{r}-r^3$ The first particle is at a distance $r=1$, and the second, at $r=4$. The best estimate for the ratio of kinetic energies of the first and the second particle is closest to :

   1. A.$6\times 10^{-2}$
   2. B.$3\times 10^{-3}$
   3. C.$10^{-1}$
   4. D.$6\times 10^2$
   Show answer

   Answer: A

3. Q392018 · 16 Apr 2018 · Shift 1

   Two moles of helium are mixed with n moles of hydrogen. If $\frac{C_p}{Cv}=\frac{3}{2}$ for the mixture, then the value of n is :

   1. A.1
   2. B.3
   3. C.2
   4. D.3 / 2
   Show answer

   Answer: C

4. Q412018 · 16 Apr 2018 · Shift 1

   Two identical conducting spheres A and B, carry equal charge. They are separated by a distance much larger than their diameters, and the force between them is F. A third identical conducting sphere, C, is uncharged. Sphere C is first touched to A, then to B, and then removed. As a result, the force between A and B would be equal to :

   1. A.F
   2. B.$\frac{3F}{4}$
   3. C.$\frac{3F}{8}$
   4. D.$\frac{F}{2}$
   Show answer

   Answer: C

5. Q332018 · 15 Apr 2018 · Shift 1

   An automobile, travelling at $40\text{km/h}$, can be stopped at a distance of 40 m by applying brakes. If the same automobile is travelling at $80\text{km/h}$, the minimum stopping distance, in metres, is (assume no skidding) :

   1. A.45 m
   2. B.100 m
   3. C.150 m
   4. D.160 m
   Show answer

   Answer: D

6. Q352018 · 15 Apr 2018 · Shift 1

   Take the mean distance of the moon and the sun from the earth to be $0.4\times 10^6\text{km}$ and $150\times 10^6\text{km}$ respectively. Their masses are $8\times 10^{22}\text{kg}$ and $2\times 10^{30}\text{kg}$ respectively. The radius of the earth is $6400\text{km}$. Let $\Delta F_1$ be the difference in the forces exerted by the moon at the nearest and farthest points on the earth and $\Delta F_2$ be the difference in the force exerted by the sun at the nearest and farthest points on the earth. Then, the number closest to $\frac{\Delta F_1}{\Delta F_2}$ is :

   1. A.2
   2. B.$10^{-2}$
   3. C.0.6
   4. D.6
   Show answer

   Answer: A

7. Q362018 · 15 Apr 2018 · Shift 1

   A thin uniform tube is bent into a circle of radius $r$ in the vertical plane. Equal volumes of two immiscible liquids, whose densities are ${\rho }_1$ and ${\rho }_2$ (${\rho }_1>{\rho }_2$), fill half the circle. The angle $\theta$ between the radius vector passing through the common interface and the vertical is :

   1. A.$\theta ={\tan }^{-1}\pi \left(\frac{{\rho }_1}{{\rho }_2}\right)$
   2. B.$\theta ={\tan }^{-1}\frac{\pi }{2}\left(\frac{{\rho }_1}{{\rho }_2}\right)$
   3. C.$\theta ={\tan }^{-1}\left(\frac{{\rho }_1-{\rho }_2}{{\rho }_1+{\rho }_2}\right)$
   4. D.$\theta ={\tan }^{-1}\frac{\pi }{2}\left(\frac{{\rho }_1+{\rho }_2}{{\rho }_1-{\rho }_2}\right)$
   Show answer

   Answer: C

8. Q442018 · 15 Apr 2018 · Shift 1

   The energy required to remove the electron from a singly ionized Helium atom is 2.2 times the energies required to remove an electron from Helium atom. The total energy required to ionize the Helium atom completely is :

   1. A.$20eV$
   2. B.$34eV$
   3. C.$79eV$
   4. D.$109eV$
   Show answer

   Answer: C

9. Q482018 · 15 Apr 2018 · Shift 1
   
   1. A.$\tan \theta =\frac{1}{2}$
   2. B.$\tan \theta =2$
   3. C.$\tan \theta =4$
   4. D.$\tan \theta =\frac{1}{4}$
   Show answer

   Answer: A

10. Q602018 · 15 Apr 2018 · Shift 1

    The number of amplitude modulted broadcast stations that can be accomodated in a $300kHz$ band width for the highest modulating frequency $15kHz$ will be :

    1. A.20
    2. B.15
    3. C.10
    4. D.8
    Show answer

    Answer: C

11. Q322018 · 8 Apr 2018 · Shift 1
    
    1. A.
    2. B.
    3. C.
    4. D.
    Show answer

    Answer: C