most repeated questions in jee main 2020

most repeated questions in jee main 2020

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Today, we are going to cover the MOST IMPORTANT QUESTION from PHYSICS, CHEMISTRY and MATHEMATICS  chapter for exams like CBSE board, NEET, JEE MAIN & JEE ADVANCE.


First try to solve the question on your own in the allotted time (45 minutes). Then check the answers.

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STUDY EVERTHING

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TIMER:

45min

Physics (Type - 1)

1. A hoop of radius r and mass m rotating with an angular velocity ω is placed on a rough horizontal surface. The initial velocity of the centre of the hoop is zero. What will be the velocity of the centre of the hoop when it ceases to slip?

a.rω/4
b.rω/3
c.rω/2
d.rω

2. A solid spherical ball of mass M and radius R rolls without slipping down on inclined plane of length L and height h. What is the speed of its centre of mass, when the cylinder reaches its bottom?
a.√3gh/7
b.√10gh/7
c.√7gh/10
d.√3gh/4

3. A 4kg mass and 1kg mass is moving with equal kinetic energies. The ratio of their momenta is
a.3:1
b.1:1
c.4:1
d.2:1

4. If the ratio of the concentration of electrons to that of holes in a semiconductor is 9/7 and the ratio of currents is 5/3 Then, the ratio of their drift velocities is

a.9/7
b.7/15
c.5/8
d.15/7

5. A ball of mass (m) 0.5 kg is attached to the end of a string having length (L) 0.5 m. The ball is rotated on a horizontal circular path about vertical axis. The maximum tension that the string can bear is 324 N. The maximum possible value of angular velocity of ball (in radian/s) is
a. 9
b.18
c.27
d.36

6. If the momentum of a body increases by 20% , then the kinetic energy will increases by
a.20%
b.40%
c.44%
d.50%

7. A circular loop of radius 0.3 cm lies parallel to a much bigger circular loop of radius 20 cm. The centre of the smaller loop is on the axis of the bigger loop. The distance between their centres is 15 cm. If a current of 2.0 A flows through the bigger loop, then the flux linked with smaller loop is
a.9×10^-11
b.6×10^-11
c.3×10^-11
d.6.6×10^-9

8. A particle moves with simple harmonic motion in a straight line. In first τ s, after starting from rest it travels a distance a, and in next τ s it travels 2a, in same direction, then
a. amplitude of motion is 4a
b. time period of oscillations is 6τ
c.amplitude of motion is 3a
d.time period of oscillations is 8τ

9. A point source S is placed at the bottom of a transparent block of height 10 mm and refractive index 2.72. It is immersed in a lower refractive index liquid as shown in the figure. It is found that the light emerging from the block to the liquid forms a circular bright spot of diameter 11.54 mm on the top of the block. The refractive index of the liquid is

a.1.21
b.1.30
c.1.36
d.1.42

Download the detailed answer pdf of the most important questions click here 

Chemistry (Type - 2)

1. A first order reaction is 50% completed in 2.12 × 10¹²s. How much time would it take for 100% completion?
a.1.06 ×10¹²
b.4.24×10²⁴
c.infinite
d. 2.12×10¹²

2.Identify the least stable ion amongst the following.
a.Li⁺
b.Be^-
c.B^-
d.C^-

3. Froth floatation process for the concentration of ores is a practical application of
a. Adsorption
b. Absorption
c. Coagulation
d. Sedimentation

4. The product (X) and (Y) respectively are
a.Picric acid, 2,4,6-Tribromophenol
b.5-Nitrosalicylic acid, 5-bromosalicylic acid
c. o- Nitrophenol, o-bromophenol
d.3,5-Dinitrosalicylic acid, 3,5-dibromo-salicylic acid

5. The monomer of synthetic rubber is
a. Butadiene
b. Chloroprene
c. 2-methyl-1, 2-butadiene
d. 2-methyl-1, 3-butadiene

6. As per IUPAC nomenclature, the name of the complex [Co(H₂O)₄(NH₃)₂]Cl₃ is
a. tetraaquadiaminecobalt (III) chloride
b. tetraaquadiamminecobalt (III) chloride
c. diaminetetraaquacobalt (III) chloride
d. diamminetctraaquacobalt (III) chloride

7. A reaction is second order with respect to a reactant. If the concentration of the reactant is doubled, then the rate of reaction becomes
a.2 times
b.3 times
c.4 times
d.no change

8. In CH₃CH₂OH the bond that undergoes hetrolytic cleavage most readily is
a.C-C
b.C-O
c.C-H
d.O-H

9. Dissolving 120 g of urea (mol. wt. 60) in 1000 g of water gave a solution of density 1.15 g/mL. The molarity of the solution is
a.1.78 M
b.2.00 M
c.2.05 M
d.2.22 M

Download the detailed answer pdf of the most important questions click here.

Mathematics (Type - 3)

1. If A is the set of even natural numbers less than 10 and B is the set of prime numbers less than 5, then the number of relations from A to B is
a.2⁸
b. 8²
c.3⁴
d.2⁹-1

2. The number of roots of the equation x + 2tanx = π /2 inthe interval [0,2 π]
a.1
b.2
c.3
d.infinite

3. Evaluate the intergral of sin(x-a)dx/sin(x+b)
a.(x-a)cos2a - sin2alog|sin(x+a)|+ c
b. (x+a)cos2a - sin2alog|sin(x-a)| + c
c.(x+a)cos2a - sin2alog|sin(x+a)| + c
d.(x-a)cos2a - sin2alog|sin(x-a)| + c

4. If a and b are two vectors such that |a +b| = √29 and a×(2i + 3j + 4k ) = (2i + 3j + 4k )×b ,then a possible value of (a+b) .(-7i + 2j+ 3k) is
a. 0
b.3
c.4
d.8

5. The function f(x) = e^|x| is
a. continuous everywhere but not differentiable at x = 0
b. continuous and differentiable everywhere
c.not continuous at x = 0
d.None of the above

6. A straight line through a fixed point (2, 3) intersects the coordinate axes at distinct points P and Q. If O is the origin and the rectangle OPRQ is completed, then the locus of R is:
a.2x + 3y = xy
b.3x + 2y = xy
c. 3x + 2y = 6xy
d.3x + 2y = 6

7. A line L passing through the focus of the parabola y ²= 4(x - 1), intersects the parabola in two distinct points. If ’m’ be the slope of the line ‘L’ then
a.-1< m < 1
b.m <-1 or m>1 <-1 m="" or="">
c.m belongs to R
d.none of these

8. For the equation 10z²- 4iz - m = 0 where z is a complex variable and i = √-1, which of the following is true?

a.Roots are purely imaginary for all negative real values of m
b.Roots are not real for all complex numbers m
c. Roots are purely imaginary for all positive real values of m
d.None of the above

9. The Boolean expression ~(pvq)v(~p^q)
a.p
b.q
c.~q
d.~p

Download the detailed answer pdf of the most important questions click here .

Unit and measurements  most important  questions	click here
Kinamatic most important questions	click here
Law of motion most important questions	click here
Work, energy and power most important questions	click here
Nit cutoff	click here
Iiit cutoff	click here

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