JEE Main 2020 Question Paper (07-Jan-2020) (Shift 2)

Question 1

A mass of $10 \mathrm{kg}$ is suspended by a rope of length $4 \mathrm{m}$ from the ceiling. A force $F$ is applied horizontally at the mid-point of the rope such that the top half of the rope makes an angle of $45^\circ$ with the vertical. Then $F$ equals: (Take $g = 10 \mathrm{m} \mathrm{s}^{-2}$ and the rope to be massless)

Accepted Answer

$100\,\mathrm{N}$

Answer

$90\,\mathrm{N}$

Answer

$70\,\mathrm{N}$

Answer

$75\,\mathrm{N}$

Question 2

A particle of mass $m$ and charge $q$ has an initial velocity $\overrightarrow{v} = v_0 \widehat{j}$. If an electric field $\overrightarrow{E} = E_0 \widehat{i}$ and a magnetic field $\overrightarrow{B} = B_0 \widehat{i}$ act on the particle, its speed will double after a time

Accepted Answer

$\frac{\sqrt{3} m v_{0}}{q E_{0}}$

Answer

$\frac{2m v_{0}}{q E_{0}}$

Answer

$\frac{3m v_{0}}{q E_{0}}$

Answer

$\frac{\sqrt{2} m v_0}{q E_0}$

Question 3

In a building, there are $15$ bulbs of $45\,\mathrm{W}$, $15$ bulbs of $100\,\mathrm{W}$, $15$ small fans of $10\,\mathrm{W}$, and $2$ heaters of $1\,\mathrm{kW}$. The voltage of the electric main supply is $220\,\mathrm{V}$. The minimum fuse capacity (rated value) of the building will be:

Accepted Answer

$20\,\mathrm{A}$

Answer

$5\,\mathrm{A}$

Answer

$25\,\mathrm{A}$

Answer

$15\,\mathrm{A}$

Question 4

An ideal fluid flows (laminar flow) through a pipe of non-uniform diameter. The maximum and minimum diameters of the pipes are $6.4\,\mathrm{cm}$ and $4.8\,\mathrm{cm}$, respectively. The ratio of the minimum and the maximum velocities of fluid in this pipe is:

Accepted Answer

$ \frac{9}{16} $

Answer

$ \frac{\sqrt{3}}{2} $

Answer

$ \frac{3}{4} $

Answer

$ \frac{81}{256} $

Question 5

Given, $B$ is magnetic field induction, and $\mu_{0}$ is the magnetic permeability of vacuum. The dimension of $\frac{B^{2}}{2\mu_{0}}$ is:

Accepted Answer

$\mathrm{M}\mathrm{L}^{-1}\mathrm{T}^{-2}$

Answer

$\mathrm{MLT}^{-2}$

Answer

$\mathrm{ML}^2\mathrm{T}^{-1}$

Answer

$\mathrm{ML}^2\mathrm{T}^{-2}$