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.
41. What should be the angle between force and displacement for maximum work to be done?
[A] 0°
[B] 90°
[C] 180°
[D] 30°
Show Answer
Correct Answer: A [0°]
Notes:
For maximum work, the angle between force and displacement should be 0°. W = Fs Cos 0° = Fs For zero work, the angle between force and displacement should be 90°. W = Fs Cos 90° = 0
42. Which of the following laws state that the orbits of the planets are ellipses, with the Sun at one focus of the ellipse?
[A] Kepler’s First law
[B] Kepler’s Second law
[C] Kepler’s Third law
[D] None of the above
Show Answer
Correct Answer: A [Kepler’s First law]
Notes:
Kepler’s First law: It is also known as law of orbits. It states that every planet revolves around the sun in an elliptical orbit. The sun is situated at one foci of the ellipse.
43. Which of the following is incorrect:
[A] Gravitational force of attraction is independent of nature of intervening medium
[B] Gravitational forces are central forces
[C] Gravitational forces are non-conservative forces
[D] All of the above
Show Answer
Correct Answer: C [Gravitational forces are non-conservative forces]
Notes:Characteristics of Gravitational Forces:
- It is always attractive in nature.
- It is independent of the medium between the bodies.
- It holds good over a wide range of distances
- It is a central force i.e. acts along the line joining the centres of two interacting bodies
- The gravitational force between two particles is independent of the presence or absence of other bodies
- It is the weakest force in nature.
- It is a conservative force i.e. work done by it is path independent or work done in moving a particle round a closed path under the action of gravitational force is zero.
- It is an action-reaction pair.
44. What is the SI unit of acceleration due to gravity?
[A] ms-2
[B] ms-3
[C] Kgms-2
[D] ms-1
Show Answer
Correct Answer: A [ms-2]
Notes:
The acceleration due to gravity is the acceleration set up in the body when it falls freely under the effect of gravity alone. The SI unit of acceleration due to gravity is ms-2
45. Which of the following is true about the effect of altitude on the value of acceleration due to gravity?
[A] The acceleration due to gravity decreases with height
[B] The acceleration due to gravity increases with height
[C] The acceleration due to gravity is not dependent on height
[D] None of the above
Show Answer
Correct Answer: A [The acceleration due to gravity decreases with height]
Notes:
The acceleration due to gravity decreases with height. G0= g(1-2h/R) where h is the height above the surface of the earth.
46. At sea level, what is the difference between the value of acceleration due to gravity at the poles and at the equator?
[A] No difference
[B] 9.8 cm s-2
[C] 1.80 cm s-2
[D] None of the above
Show Answer
Correct Answer: C [1.80 cm s-2]
Notes:
At sea level, the difference between the value of acceleration due to gravity at the poles and at the equator is 1.80 cm s-2. The value of acceleration due to gravity increases as we go from equator to the poles.
47. Which of the following statements is correct about the value of acceleration due to gravity (g) in a light and heavy falling body?
[A] the value of g will be greater in the light body
[B] the value of g will be greater in the heavy body
[C] the value of g will be equal in both the bodies
[D] the value of g depends on the mass
Show Answer
Correct Answer: C [the value of g will be equal in both the bodies]
Notes:
Acceleration due to gravity is independent of mass, shape, size etc. of falling body. Therefore, a light and heavy body will have equal acceleration.
48. What will be the change in the force of attraction between two bodies if the distance between them is doubled?
[A] No change
[B] Becomes double
[C] Becomes four times
[D] Becomes nine times
Show Answer
Correct Answer: C [Becomes four times]
Notes:
If the distance between two masses is doubled, the gravitational attraction between them becomes 4 times. F = Gm1m2/r2
49. What is the height of geo-stationary satellites from the surface of the earth?
[A] 30000 km
[B] 36000 km
[C] 48000 km
[D] 72000 km
Show Answer
Correct Answer: B [36000 km]
Notes:
The satellite which appears stationary relative to earth is called a geostationary satellite. A geostationary satellite always stays over the same place above the earth. Such a satellite appears stationary due to its zero relative velocity w.r.t. that place on earth. The height of geo-stationary satellites from the surface of the earth is 36000 km.
50. The time period of a satellite does not depend on which of the following?
[A] Radius of earth
[B] Height of the satellite
[C] Mass of the satellite
[D] None of the above
Show Answer
Correct Answer: C [Mass of the satellite]
Notes:
Time period of a satellite is the time taken by satellite to go once around the earth. The time period is independent of the mass of orbiting body and depends on the mass of central body and radius of the orbit.
Advertisement
