Centre of Mass & Rotational Motion · JEE Main previous year questions

2018 8 questions

1. Q362018 · 16 Apr 2018 · Shift 1

   Suppose that the angular velocity of rotation of earth is increased. Then, as a consequence :

   1. A.Weight of the object, everywhere on the earth, will increase.
   2. B.Weight of the object, everywhere on the earth, will decrease.
   3. C.There will be no change in weight anywhere on the earth.
   4. D.Except at poles, weight of the object on the earth will decrease.
   Show answer

   Answer: D

2. Q452018 · 16 Apr 2018 · Shift 1

   A charge q is spread uniformly over an insulated loop of radius r. If it is rotated with an angular velocity $\omega$ with resect to normal axis then the magnetic moment of the loop is :

   1. A.$q\omega r^2$
   2. B.$\frac{4}{3}q\omega r^2$
   3. C.$\frac{3}{2}q\omega r^2$
   4. D.$\frac{1}{2}q\omega r^2$
   Show answer

   Answer: D

3. Q532018 · 16 Apr 2018 · Shift 1
   
   1. A.1 : 3
   2. B.1 : 4
   3. C.1 : 5
   4. D.1 : 2
   Show answer

   Answer: A

4. Q542018 · 15 Apr 2018 · Shift 1
   
   1. A.$m,x$
   2. B.$m,\frac{1}{x}$
   3. C.$m,\frac{1}{x^2}$
   4. D.$m,x^2$
   Show answer

   Answer: B

5. Q352018 · 8 Apr 2018 · Shift 1
   
   1. A.$\frac{181}{2}M{R}^2$
   2. B.$\frac{55}{2}M{R}^2$
   3. C.$\frac{19}{2}M{R}^2$
   4. D.$\frac{73}{2}M{R}^2$
   Show answer

   Answer: A

6. Q362018 · 8 Apr 2018 · Shift 1
   
   1. A.$\frac{37}{9}M{R}^2$
   2. B.$4M{R}^2$
   3. C.$\frac{40}{9}M{R}^2$
   4. D.$10M{R}^2$
   Show answer

   Answer: B

7. Q372018 · 8 Apr 2018 · Shift 1

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

   1. A.$\mathrm{T}\propto {\mathrm{R}}^{\mathrm{n}/2}$
   2. B.$\mathrm{T}\propto {\mathrm{R}}^{3/2}$ for any n
   3. C.$\mathrm{T}\propto {\mathrm{R}}^{\mathrm{n}/2+1}$
   4. D.$\mathrm{T}\propto {\mathrm{R}}^{(\mathrm{n}+1)/2}$
   Show answer

   Answer: D

8. Q432018 · 8 Apr 2018 · Shift 1

   A granite rod of 60 cm length is clamped at its middle point and is set into longitudinal vibrations. The density of granite is $2.7\times 10^{3}kg/{\mathrm{m}}^3$ and its Young’s modulus is $9.27\times 10^{10}\mathrm{Pa}$. What will be the fundamental frequency of the longitudinal vibrations ?

   1. A.$7.5\mathrm{kHz}$
   2. B.$5\mathrm{kHz}$
   3. C.$2.5\mathrm{kHz}$
   4. D.$10\mathrm{kHz}$
   Show answer

   Answer: B