Practice problems on JEE Mains, JEE Mains 2021 July 20 Shift 2

Question 1

Consider the following three statements :(A) If 3 + 3 = 7 then 4 + 3 = 8.(B) If 5 + 3 = 8 then earth is flat.(C) If both (A) and (B) are true then 5 + 6 = 17.Then which of the following statements is correct ?

Accepted Answer

(A) and (C) are true while (B) is false

Answer

(A) and (B) are false while (C) is true

Answer

(A) is false, but (B) and (C) is true

Answer

(A) is true while (B) and (C) are false

Question 2

The single largest industrial application of dihydrogen is :

Accepted Answer

In the synthesis of ammonia

Answer

Rocket fuel in space research

Answer

Manufacture of metal hydrides

Answer

In the synthesis of nitric acid

Question 3

In Carius method, halogen containing organic compound is heated with fuming nitric acid in the presence of :

Accepted Answer

AgNO3​

Answer

BaSO4​

Answer

HNO3​

Answer

CuSO4​

Question 4

A boy reaches the airport and finds that the escalator is not working. He walks up the stationary escalator in time t1​. If he remains stationary on a moving escalator then the escalator takes him up in time t2​. The time taken by him to walk up on the moving escalator will be :

Accepted Answer

t2​+t1​t1​t2​​

Answer

t2​−t1​

Answer

t2​−t1​t1​t2​​

Answer

2t1​+t2​​

Question 5

The correct order of their reactivity towards hydrolysis at room temperature is :

Accepted Answer

(A) > (B) > (C) > (D)

Answer

(D) > (A) > (B) > (C)

Answer

(A) > (C) > (B) > (D)

Answer

(D) > (B) > (A) > (C)

Question 6

If the mean and variance of six observations 7,10,11,15, a, b are 10 and 320​, respectively, then the value of |a – b| is equal to :

Accepted Answer

1

Answer

9

Answer

7

Answer

11

Question 7

The length of a metal wire is l1​, when the tension in it is T1​ and is l2​ when the tension is T2​. The natural length of the wire is :

Accepted Answer

T2​−T1​I1​ T2​−I2​ T1​​

Answer

I1​I2​​

Answer

2I1​+I2​​

Answer

T2​+T1​I1​ T2​+I2​ T1​​

Question 8

Consider the line L given by the equation 2x−3​=1y−1​=1z−2​. Let Q be the mirror image of the point (2,3,–1) with respect to L. Let a plane P be such that it passes through Q, and the line L is perpendicular to P. Then which of the following points is on the plane P ?

Accepted Answer

(1, 2, 2)

Answer

(1, 1, 1)

Answer

(–1, 1, 2)

Answer

(1, 1, 2)

Question 9

A body rolls down an inclined plane without slipping. The kinetic energy of rotation is 50% of its translational kinetic energy. The body is :

Accepted Answer

Solid cylinder

Answer

Hollow cylinder

Answer

Solid sphere

Answer

Ring

Question 10

Which one of the following statement is not true about enzymes ?

Accepted Answer

Enzymes are non-specific for a reaction and substrate

Answer

Almost all enzymes are proteins

Answer

The action of enzymes is temperature and pH specific

Answer

Enzymes work as catalysis by lowering the activation energy of a biochemical reaction

Question 11

A body at rest is moved along a horizontal straight line by a machine delivering a constant power. The distance moved by the body in time 't' is proportional to :

Accepted Answer

t23​

Answer

t21​

Answer

t41​

Answer

t43​

Question 12

In an electromagnetic wave the electric field vector and magnetic field vector are given as E=E0​i^ and B=B0​k^ respectively. The direction of propagation of the electromagnetic wave is along :

Accepted Answer

(−j^​)

Answer

j^​

Answer

(−k^)

Answer

k^