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. What will be the work done in holding a 25 kg iron plate for 25 seconds?
[A] 25 j
[B] 1 j
[C] 0
[D] 625 j
Show Answer
Correct Answer: C [0]
Notes:
The work done in holding a 25 kg iron plate for 25 seconds will be zero as there is no displacement taking place. Work done = Force x Displacement
32. What is the coefficient of restitution for a perfectly elastic collision?
Show Answer
Correct Answer: B [1]
Notes:
For a perfectly elastic collision, the coefficient of restitution is equal to 1 as the velocity of separation after collision is equal to the velocity of approach before collision. For a perfectly inelastic collision, the coefficient of restitution is equal to 0 as the velocity of separation after collision is equal to 0. The coefficient of restitution or coefficient of resilience is the ratio of relative velocity of separation after collision and the velocity of approach before collision.
33. What is the effect on velocities of the two bodies of equal masses when they undergo elastic collision in one dimension?
[A] remains same
[B] gets interchanged
[C] becomes twice of the original velocity
[D] becomes half of the original velocity
Show Answer
Correct Answer: B [gets interchanged]
Notes:
The velocities get interchanged when two bodies of equal masses undergo elastic collision in one dimension.
34. What happens to the velocity of a light body when it undergoes an elastic collision in one dimension with a very heavy body at rest?
[A] its velocity becomes twice
[B] it rebounds with twice of its own velocity
[C] it rebounds with its own velocity
[D] it stops and comes to rest
Show Answer
Correct Answer: C [it rebounds with its own velocity]
Notes:
A light body rebounds with its own velocity when it undergoes an elastic collision in one dimension with a very heavy body at rest. Note: The heavy body continues to be in rest in this case
35. Which of the following is true about universal gravitational constant in the case of two bodies each of unit mass having their centres placed at unit distance apart?
[A] It is equal to the force of attraction between them
[B] It is equal to twice the force of attraction between them
[C] It is equal to half the force of attraction between them
[D] It is equal to ten times the force of attraction between them
Show Answer
Correct Answer: A [It is equal to the force of attraction between them]
Notes:
The universal gravitational constant is equal to the force of attraction between two bodies each of unit mass having their centres placed at unit distance apart. F = Gm1m2/r When m1 and m2 = 1 and r=1 then F=G.
36. Which of the following represents the dimensional formula of Universal Gravitational Constant?
[A] M1 L2 T-2
[B] M-1 L1 T-2
[C] M-1 L3 T-2
[D] M1 L3 T-2
Show Answer
Correct Answer: C [M-1 L3 T-2]
Notes:
The dimensional formula of Universal Gravitational Constant is M-1 L3 T-2 Universal Gravitational Constant is a scalar quantity.
37. 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.
38. Which of the following is correct about acceleration due to gravity?
[A] it increases with depth
[B] it decreases with depth
[C] it is independent of depth
[D] None of the above
Show Answer
Correct Answer: B [it decreases with depth]
Notes:
The value of acceleration due to gravity decreases with depth. g0= g(1-d/R) where d is the depth below the centre of the earth.
39. What will be the effect on the value of acceleration due to gravity at the poles if the rate of rotation of earth increases?
[A] No effect
[B] it will increase
[C] it will decrease
[D] it will become zero
Show Answer
Correct Answer: A [No effect]
Notes:
If the rate of rotation of earth increases then the value of acceleration due to gravity decreases at all the places on the surface of earth except at poles.
40. 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
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