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.
21. Which of the following statements is correct?
[A] Bulk stress occurs only in liquids
[B] Longitudinal stress occurs only in solids
[C] Both a and b
[D] None of the above
Show Answer
Correct Answer: B [Longitudinal stress occurs only in solids]
Notes:
Longitudinal stress occurs only in solids. It comes in picture only when one of the three dimensions viz. length, breadth, height is much greater than other two.
22. What is the maximum stress after which the wire breaks called as?
[A] Tensile strength
[B] Shear strength
[C] Bulk strength
[D] Hooke’s strength
Show Answer
Correct Answer: A [Tensile strength]
Notes:
The maximum stress after which the wire begin to flow and breaks, is called breaking stress or tensile strength. The force by application of which the wire breaks is called the breaking force.
23. On which of the following factors the breaking stress depends?
[A] Area of cross-section
[B] length of the material
[C] Nature of the material
[D] None of the above
Show Answer
Correct Answer: C [Nature of the material]
Notes:
Breaking force = P × A Here P is a constant of proportionality and known as breaking stress. Breaking stress is constant for a given material and does not depend upon the dimension (length or thickness) of wire.
24. What happens to a body when its density is equal to the density of the fluid?
[A] it floats
[B] it sinks
[C] it remains suspended
[D] None of the above
Show Answer
Correct Answer: C [it remains suspended]
Notes:
If the buoyant force equals the object’s weight, the object will remain suspended at that depth. If the buoyant force is greater than the object’s weight, the object will rise to the surface and float. If the buoyant force is less than the object’s weight, the object will sink. The buoyant force is always present whether the object floats, sinks, or is suspended in a fluid.
25. Which of the following is equal to the upthrust of the body?
[A] mass of body
[B] weight of liquid
[C] weight of liquid displaced
[D] density of liquid
Show Answer
Correct Answer: C [weight of liquid displaced]
Notes:
Archimedes Principle: when a body is immersed partially or completely in a liquid, it experiences an upthrust, which is equal to the weight of the liquid displaced by the body.
26. Which of the following intermolecular forces enables us to write on the blackboard with a chalk?
[A] Cohesive force
[B] Adhesive force
[C] both a and b
[D] None
Show Answer
Correct Answer: B [Adhesive force]
Notes:
The force of attraction between the molecules of the different substances is called the force of adhesion. Adhesive force enables us to write on the blackboard with a chalk.
27. Which of the following instruments is used to measure the relative density of a liquid?
[A] Hydrometer
[B] Hygrometer
[C] Lactometer
[D] Gravitimeter
Show Answer
Correct Answer: A [ Hydrometer ]
Notes:
A hydrometer is an instrument used to measure the specific gravity or relative density of liquids, i.e. the ratio of the density of the liquid to the density of water.
28. Which of these instruments is used for testing the purity of milk?
[A] Hydrometer
[B] Lactometer
[C] Galvanometer
[D] Ammeter
Show Answer
Correct Answer: B [ Lactometer ]
Notes:
Lactometer is used for measuring the relative density of milk and hence testing the purity of milk. It is a specially designed hydrometer.
29. Which of the following is correct about the density of sea water?
[A] it is more than fresh water
[B] it is less than fresh water
[C] it is equal to the density of fresh water
[D] None of the above
Show Answer
Correct Answer: A [ it is more than fresh water ]
Notes:
The density of sea water is more than fresh water. The density of sea water is 1.06 × 103 kg m–3 and that of fresh water is 1.0 × 103 kg m–3.
30. What is the density of air at room temperature?
[A] 1.41
[B] 1.75
[C] 1.29
[D] 1.9
Show Answer
Correct Answer: C [ 1.29 ]
Notes:
The density of air at room temperature near the surface of the Earth is approximately 1.29 kg/m3.
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