Questions and answers for exam Preparation

MCQs

Total Questions : 150 | Page 8 of 15 pages

Question 71. Assertion (A) : A man standing on a completely frictionless surface can propel himself by whistling.
Reason (R) : If no external force acts on a system, its momentum cannot change. Codes

Both A and R are true and R is the correct explanation of A
Both A and R are true but R is not a correct explanation of A
A is true but R is false
A is false but R is true

Discuss Question

Answer: Option C. -> A is true but R is false
:
C
Option:(c)

Question 72. Consider the following statements A simple pendulum is set into oscillation. Then
1.The acceleration is zero when the bob passes through the mean position.
2.In each cycle the bob attains a given velocity twice.
3.Both acceleration and velocity of the bob are zero when it reaches its extreme position during the oscillation.
4.The amplitude of oscillation of the simple pendulum decreases with time.
Which of these statements are correct?

1 and 2
3 and 4
1, 2 and 4
2, 3 and 4

Discuss Question

Answer: Option C. -> 1, 2 and 4
:
C
Option:(c)

Question 73. The mass of a body on earth is 100 kg (acceleration due to gravity, g_e =10 m/s². If acceleration due to gravity on the moon is g_e /6, then the mass of the body on the moon is

100/6 kg
60 kg
100 kg
600 kg

Discuss Question

Answer: Option C. -> 100 kg
:
C
Option:(c)

Question 74. Which of the following distance-time graph (x-t) represents one-dimensional uniform motion?

Discuss Question

Answer: Option C. -> 100 kg
:
D
Option:(d)

Question 75. Assertion (A): Small glass beads fixed on traffic signals glow brightly when light falls upon them.
Reason (R): Light is totally reflected when the angle of incidence exceeds a certain critical value and light travelling in a denser medium is reflected from a rarer medium.
Codes

Both A and R are true and R is the correct explanation of A
Both A and R are true but R is not a correct explanation of A
A is true but R is false
A is false but R is true

Discuss Question

Answer: Option A. -> Both A and R are true and R is the correct explanation of A
:
A
Option:(a)

Question 76. Barium in a suitable form is administered to patients before an X-ray examination of the stomach, because

barium allows X-rays to pass through the stomach on account of its transparency to X-rays
barium compound, like magnesium sulphate helps in cleaning the stomach before X-ray examination
barium is a good absorber of X-rays and this helps the stomach to appear clearly in contrast with the other regions in the picture
barium salts are white in colour and this helps the stomach to appear clearly in contrast with other regions in the picture

Discuss Question

Answer: Option C. -> barium is a good absorber of X-rays and this helps the stomach to appear clearly in contrast with the other regions in the picture
:
C
Option:(c)

Question 77. Paper becomes brittle and yellow with age. Why?
1.The acid content in paper causes brittleness to develop
2.In the presence of visible light, photosensitized oxidation occurs
3.The ultra-violet component of sunlight causes photolysis of cellulose by direct cleavage of the cellulose polymer

1 and 2
2 and 3
1 and 3
1, 2 and 3

Discuss Question

Answer: Option D. -> 1, 2 and 3
:
D
Option:(d)

Question 78. Which one of the following is the correct sequence of the given substances in the decreasing order of their densities?

Steel > Mercury > Gold
Gold > Mercury > Steel
Steel > Gold > Mercury
Gold > Steel > Mercury

Discuss Question

Answer: Option B. -> Gold > Mercury > Steel
:
B
Option:(b)

Question 79. What is the correct ascending order for frequencies of the following radiations?
1.Visible
2.X-rays
3.Ultraviolet
4.Radio waves

1, 2, 3, 4
3, 2, 4, 1
4, 1, 3, 2
4, 3, 1, 2

Discuss Question

Answer: Option C. -> 4, 1, 3, 2
:
C
Option:(c)

Question 80. Assertion (A) : In our houses, the current in A.C. electricity line changes direction 60 times per second.
Reason (R) : The frequency of alternating voltage supplied is 50 Hz.
Codes