JEE MAIN - Physics (2020 - 6th September Morning Slot)

1
Identify the correct output signal Y in the given combination of gates (as shown) for the given inputs A and B.
پاسخ دهید
(D)
2
A particle of charge q and mass m is moving with a velocity $$ - v\widehat i$$ (v $$ \ne $$ 0) towards a large screen placed in the Y - Z plane at a distance d. If there is a magnetic field $$\overrightarrow B = {B_0}\widehat k$$ , the maximum value of v for which the particle will not hit the screen is :
پاسخ دهید
(D)
$${{qd{B_0}} \over {m}}$$
3
Two bodies of the same mass are moving with the same speed, but in different directions in a plane. They have a completely inelastic collision and move together thereafter with a final speed which is half of their initial speed. The angle between the initial velocities of the two bodies (in degree) is ________.
پاسخ دهید
120
4
Molecules of an ideal gas are known to have three translational degrees of freedom and two rotational degrees of freedom.The gas is maintained at a temperature of T. The total internal energy, U of a mole of this gas, and the value of
$$\gamma \left( { = {{{C_p}} \over {{C_v}}}} \right)$$ are given, respectively by:
پاسخ دهید
(A)
U = $${5 \over 2}RT$$ and $$\gamma = {7 \over 5}$$
5
An object of mass m is suspended at the end of a massless wire of length L and area of crosssection A. Young modulus of the material of the wire is Y. If the mass is pulled down slightly its frequency of oscillation along the vertical direction is :
پاسخ دهید
(A)
$$f = {1 \over {2\pi }}\sqrt {{{YA} \over {mL}}} $$
6
A point like object is placed at a distance of 1 m in front of a convex lens of focal length 0.5 m. A plane mirror is placed at a distance of 2 m behind the lens. The position and nature of the final image formed by the system is :
پاسخ دهید
(A)
2.6 m from the mirror, real
7
An insect is at the bottom of a hemispherical ditch of radius 1 m. It crawls up the ditch but starts slipping after it is at height h from the bottom. If the coefficient of friction between the ground and the insect is 0.75, then h is :
(g = 10 ms^–2)
پاسخ دهید
(C)
0.20 m
8
In the figure below, P and Q are two equally intense coherent sources emitting radiation of wavelength 20 m. The separation between P and Q is 5 m and the phase of P is ahead of that of Q by 90^o. A, B and C are three distinct points of observation, each equidistant from the midpoint of PQ. The intensities of radiation at A, B, C will be in the ratio :

پاسخ دهید
(B)
2 : 1 : 0
9
A clock has a continuously moving second's hand of 0.1 m length. The average acceleration of the tip of the hand (in units of ms^–2) is of the order of :
پاسخ دهید
(A)
10^-3
10
Charges Q₁ and Q₂ are at points A and B of a right angle triangle OAB (see figure). The resultant electric field at point O is perpendicular to the hypotenuse, then
$${{{Q_1}} \over {{Q_2}}}$$ is proportional to :
پاسخ دهید
(C)
$${{{x_1}} \over {{x_2}}}$$
11
An electron is moving along +x direction with a velocity of 6 $$ \times $$ 10⁶ ms^–1. It enters a region of uniform electric field of 300 V/cm pointing along +y direction. The magnitude and direction of the magnetic field set up in this region such that the electron keeps moving along the x direction will be :
پاسخ دهید
(C)
5 $$ \times $$ 10^–3 T, along +z direction
12
Shown in the figure is a hollow icecream cone (it is open at the top). If its mass is M, radius of its top, R and height, H, then its moment of inertia about its axis is :
پاسخ دهید
(B)
$${{M{R^2}} \over 2}$$
13
You are given that Mass of $${}_3^7Li$$ = 7.0160u,
Mass of $${}_2^4He$$ = 4.0026u
and Mass of $${}_1^1H$$ = 1.0079u.
When 20 g of $${}_3^7Li$$ is converted into $${}_2^4He$$ by proton capture, the energy liberated, (in kWh), is :
[Mass of nucleon = 1 GeV/c²]
پاسخ دهید
(D)
1.33 $$ \times $$ 10⁶
14
If the potential energy between two molecules is given by
U = $$ - {A \over {{r^6}}} + {B \over {{r^{12}}}}$$,
then at equilibrium, separation between molecules, and the potential energy are :
پاسخ دهید
(A)
$${\left( {{{2B} \over A}} \right)^{1/6}}$$, $$ - {{{A^2}} \over {4B}}$$
15
A satellite is in an elliptical orbit around a planet P. It is observed that the velocity of the satellite when it is farthest from the planet is 6 times less than that when it is closest to the planet. The ratio of distances between the satellite and the planet at closest and farthest points is:
پاسخ دهید
(C)
1 : 6
16
For the given input voltage waveform V_in(t), the output voltage waveform V₀(t), across the capacitor is correctly depicted by :
پاسخ دهید
(B)
17
Four point masses, each of mass m, are fixed at the corners of a square of side $$l$$. The square is rotating with angular frequency $$\omega $$, about an axis passing through one of the corners of the square and parallel to its diagonal, as shown in the figure. The angular momentum of the square about this axis is :
پاسخ دهید
(A)
3m$$l$$²$$\omega $$
18
A screw gauge has 50 divisions on its circular scale. The circular scale is 4 units ahead of the pitch scale marking, prior to use. Upon one complete rotation of the circular scale, a displacement of 0.5mm is noticed on the pitch scale. The nature of zero error involved and the least count of the screw gauge, are respectively :
پاسخ دهید
(C)
Positive, 10 $$\mu $$m
19
An electron, a doubly ionized helium ion (He⁺⁺) and a proton are having the same kinetic energy. The relation between their respective de-Broglie wavelengths $$\lambda $$_e, $$\lambda $$_He⁺⁺ and $$\lambda $$_p is :
پاسخ دهید
(C)
$$\lambda $$_e > $$\lambda $$_p > $$\lambda $$_He⁺⁺
20
A part of a complete circuit is shown in the figure. At some instant, the value of current I is 1A and it is decreasing at a rate
of 10² A s^–1. The value of the potential difference V_P – V_Q , (in volts) at that instant, is _________.

پاسخ دهید
33
21
Initially a gas of diatomic molecules is contained in a cylinder of volume V₁ at a pressure P₁ and temperature 250 K. Assuming that 25% of the molecules get dissociated causing a change in number of moles. The pressure of the resulting gas at temperature 2000 K, when contained in a volume 2V₁ is given by P₂ . The ratio $${{{P_2}} \over {{P_1}}}$$ is ________.
پاسخ دهید
5
22
The density of a solid metal sphere is determined by measuring its mass and its diameter. The maximum error in the density of the sphere is $$\left( {{x \over {100}}} \right)$$ %. If the relative errors in measuring the mass and the diameter are 6.0% and 1.5% respectively, the value of x is_______.
پاسخ دهید
1050
23
A particle of charge q and mass m is moving with a velocity $$ - v\widehat i$$ (v $$ \ne $$ 0) towards a large screen placed in the Y - Z plane at a distance d. If there is a magnetic field $$\overrightarrow B = {B_0}\widehat k$$ , the maximum value of v for which the particle will not hit the screen is :
پاسخ دهید
(D)
$${{qd{B_0}} \over {m}}$$