General Science - Physics
Welcome to General Science – Physics MCQ series of GKToday. As of today February 26, 2020, this series has 590 Questions. You may purchase a PDF E-Book compilation comprising all these questions and their answers with explanation from this link.
41. What is the upward force experienced by a body, when it is immersed in a fluid, known as?
[A] Tangential force
[B] Buoyant force
[C] Centrifugal force
[D] Hydraulic force
Show Answer
Correct Answer: B [Buoyant force]
Notes:
When a body is immersed in a fluid (liquid or gas) it exerts an upward force on that body. This upward force is called up thrust or buoyant force, The whole phenomenon is called as buoyancy.
42. 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.
43. What will be the buoyant force acting on the stone, on being immersed in water, if it displaces 100gms of water?
[A] 1000 gm-weight
[B] 100 gm-weight
[C] 10 gm-weight
[D] 1 gm-weight
Show Answer
Correct Answer: B [100 gm-weight]
Notes:
As per Archimedes’ principle, if a stone, on being immersed in water, displaces 100gms of water, the buoyant force acting on the stone will be equal to 100gm-weight.
44. What will be the change in the height of water in a capillary tube in stationary condition on earth if the same tube is taken in a lift going downward with acceleration?
[A] height increases
[B] height decreases
[C] Remains same
[D] can decrease or increase
Show Answer
Correct Answer: A [height increases]
Notes:
In a lift going downward with acceleration, the effective acceleration decreases. So height increases as height is inversely proportional to the acceleration due to gravity.
45. Which of the following is NOT an example of capillary action?
[A] Rise of ink in the fine pores of blotting paper
[B] soaking of water by a towel
[C] Wood swells in rainy season due to rise of moisture
[D] None of the above
Show Answer
Correct Answer: D [None of the above]
Notes:
Examples of capillarity : (i) Ink rises in the fine pores of blotting paper leaving the paper dry. (ii) A towel soaks water. (iii) Oil rises in the long narrow spaces between the threads of a wick. (iv) Wood swells in rainy season due to rise of moisture from air in the pores.
46. What is the relationship between excess pressure and the radius of the bubble?
[A] are equal in value
[B] inversely proportional to each other
[C] directly proportional to each other
[D] no relationship
Show Answer
Correct Answer: B [inversely proportional to each other]
Notes:
Excess pressure is inversely proportional to the radius of bubble (or drop). It means that the pressure inside a smaller bubble is higher than inside a larger bubble.
47. What is the angle of contact for pure water and glass?
[A] 0°
[B] 30°
[C] 180°
[D] 90°
Show Answer
Correct Answer: A [0°]
Notes:
Angle of contact between a liquid and a solid is defined as the angle enclosed between the tangents to the liquid surface and the solid surface inside the liquid, both the tangents being drawn at the point of contact of the liquid with the solid. Its value lies between 0° and 180°: 0°for pure water and glass, 8°for tap water and glass, 90° for water and silver
48. Which of the following is the S.I. unit of density?
[A] m-2
[B] m-3
[C] kg m-2
[D] kg m-3
Show Answer
Correct Answer: D [ kg m-3 ]
Notes:
The SI unit of density is kg m-3. It is a positive scalar quantity. The Gaussian unit of density is the gram per cubic centimeter which is equivalent to a gram per milliliter [1 g/cm3 = 1 g/ml].
49. 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.
50. What do we call the maximum velocity of a fluid in a tube for which the flow remains streamlined?
[A] Hyper velocity
[B] critical velocity
[C] stream velocity
[D] laminar velocity
Show Answer
Correct Answer: B [critical velocity]
Notes:
The maximum velocity of a fluid in a tube for which the flow remains streamlined is called its critical velocity.
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