General Science - Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examinations.
31. Which of the following has an effect on the value of acceleration due to gravity?
[A] Shape of the earth
[B] Height above the earth surface
[C] Axial rotation of the earth
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
The value of acceleration due to gravity vary due to the following factors : (a) Shape of the earth (b) Height above the earth surface (c) Depth below the earth surface (d) Axial rotation of the earth
32. What do we call the minimum velocity with which a body must be projected up, so as to enable it to just overcome the gravitational pull?
[A] Orbital velocity
[B] Gravitational velocity
[C] Escape velocity
[D] None of the above
Show Answer
Correct Answer: C [Escape velocity]
Notes:
The minimum velocity with which a body must be projected up, so as to enable it to just overcome the gravitational pull, is known as Escape velocity. Ve = (2gR)1/2
33. The minimum speed required to put a satellite into a given orbit around earth is known as:
[A] Escape velocity
[B] Orbital velocity
[C] Kinetic velocity
[D] None of the above
Show Answer
Correct Answer: B [Orbital velocity]
Notes:
The minimum speed required to put a satellite into a given orbit around earth is known as Orbital velocity of the satellite. Orbital velocity (v) = (GM/r)1/2 where G= gravitational constant, M= mass of the earth and r = radius of the orbit of the satellite.
34. The angular momentum of a satellite depends on which of the following?
[A] Mass of the satellite
[B] Mass of the planet
[C] Radius of orbit of satellite
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
The angular momentum of a satellite depends on: 1. Mass of the satellite 2. Mass of the planet 3. Radius of orbit of satellite it is denoted by L. L = (m2GMr)1/2
35. Water does not fall out of a glass when it is inverted inside a satellite, which is orbiting very close to the earth’s surface. Which of the following is the best reason for this?
[A] The earth does not exert any force on the water
[B] The earth’s force of attraction on the water is exactly balanced by the force created by the satellites
[C] The water and the glass have the same acceleration due to gravity
[D] The gravitational attraction between the glass and the water balances the earth’s attraction on the
Show Answer
Correct Answer: C [The water and the glass have the same acceleration due to gravity]
Notes:
Water does not fall out of a glass when it is inverted inside a satellite, which is orbiting very close to the earth’s surface. The reason for this is that the water and the glass have the same acceleration due to gravity, equal to g, towards the centre of the earth. Hence there is no relative motion between them.
36. By how much times the orbital speed of a satellite needs to be increased to make it escape the gravitational field?
[A] √3 times
[B] 4 times
[C] 2 times
[D] √2 times
Show Answer
Correct Answer: D [√2 times]
Notes:
It means that if the speed of a satellite orbiting close to the earth is made √2 times (or increased by 41%) then it will escape from the gravitational field.
37. What is the effect of increase in radius of orbit on the binding energy of a satellite?
[A] it increases
[B] it decreases
[C] It remains the same
[D] None of the above
Show Answer
Correct Answer: B [it decreases]
Notes:
The binding energy of a satellite decreases with the increase in the radius of orbit. The binding energy of a satellite is inversely proportional to the radius of orbit.
38. What will happen to a ball if it is dropped from a spacecraft revolving around the earth at a height of 120 km?
[A] It will go very far in the space
[B] It will fall down to the earth gradually
[C] If will move with the same speed tangentially to the spacecraft
[D] It will continue to move with velocity v along the original orbit of spacecraft
Show Answer
Correct Answer: D [It will continue to move with velocity v along the original orbit of spacecraft]
Notes:
If a ball is dropped from a spacecraft revolving around the earth at a height of 120 km, it will continue to move with velocity v along the original orbit of spacecraft. As the ball possess same initial tangential speed as that of space craft. So, it also feels the condition of weightlessness.
39. Which of these states of matter has the maximum density?
[A] Solids
[B] Liquids
[C] Gases
[D] None of the above
Show Answer
Correct Answer: A [Solids]
Notes:
The density is maximum in case of solids. In the case of liquids, the density is less than solids but more than gases. In gases, the density is minimum.
40. What is the fourth state of matter called?
[A] Solid
[B] Liquid
[C] Gas
[D] Plasma
Show Answer
Correct Answer: D [Plasma]
Notes:
The fourth state of matter is called as Plasma. In Plasma, the medium is in the form of positive and negative ions. Plasma occurs in the atmosphere of stars (including the sun) and in discharge tubes.
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