Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
1. The value of acceleration due to gravity is __________?
[A] Minimum at equator and maximum at poles
[B] maximum at equator and minimum at poles
[C] equal at poles and equator
[D] None of the above
Show Answer
Correct Answer: A [Minimum at equator and maximum at poles]
Notes:
The value of acceleration due to gravity is maximum at equator. This is because the distance from the center is minimum at the equator.
2. Which of the following waves can be used to measure the speed of a approaching car?
[A] Light waves
[B] Micro waves
[C] Radio waves
[D] Sound waves
Show Answer
Correct Answer: C [Radio waves]
Notes:
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as high as 300 gigahertz to as low as 30 hertz. It is used to measure the speed of an approaching car.
3. Mach number is a measure of which of the following?
[A] Speed
[B] Heat Transfer
[C] Static Pressure
[D] Volume
Show Answer
Correct Answer: A [Speed]
Notes:
Mach number refers to the ratio of the velocity of a fluid to the velocity of sound in that fluid, named after Ernst Mach (1838–1916), an Austrian physicist and philosopher. Speed of sound is Mach 1 speed.
4. A small quantity of water is placed in a small cavity made in a block of Ice at 0 degree centigrade. Which of the following will happen?
[A] the temperature of water will become zero and it will freeze
[B] the temperature of water will become zero but it will not freeze
[C] the temperature of the water will become zero and it will come out of the cavity
[D] the temperature of the water will become zero and ice will melt to merge with water
Show Answer
Correct Answer: B [the temperature of water will become zero but it will not freeze]
Notes:
When a small quantity of water is placed in a small cavity made in a block of Ice at 0 degree centigrade the temperature of water will become zero but it will not freeze.
5. At which of the following places water shall boil at the lowest temperature?
[A] Kochi
[B] Ooty
[C] Mount Abu
[D] New Delhi
Show Answer
Correct Answer: B [Ooty]
Notes:
This question is related to Antoine equation. Water to get boil, its vapour pressure must reach to its surrounding pressure. In a pressure cooker, it boils at the highest temperature. Elevation of Kochi is 0 m, ooty is 2,486 m, Mount Abu is 1,200 m, New Delhi is 216 m, Shimla is 2,205 m. So comparing all of them, water will boil at lowest temperature at ooty, followed by Shimla, Mount Abu , New Delhi and Kochi. This is because , higher we go lower is the atmospheric pressure and lower is the point where water`s vapour pressure gets equal to the atmospheric pressure.
6. Whenever there are high winds, such as in storms, thin metal roofs on sheds as well as concave roofs on huts are sometimes blown away. Which among the following explains this correctly?
[A] During windstorm , the atmospheric pressure above the roof is very high in comparison to below the roof
[B] During windstorm , the atmospheric pressure above the roof is very low in comparison to below the roof
[C] The high velocity wind exerts tangential force on the roof surface
[D] The high velocity wind exerts vertical force on the roof surface
Show Answer
Correct Answer: B [During windstorm , the atmospheric pressure above the roof is very low in comparison to below the roof]
Notes:
During the storm, the velocity of wind above the roof surface is very high and hence pressure is low. The pressure below the roof is atmospheric which is higher than the pressure of upper surface. Due to this pressure difference, the roof blows.
7. Which of the following is NOT correct about units of work:
[A] 1 joule = 107 ergs
[B] 1 kg-m = 1 joule
[C] 1 kg-m = 9.8 joule
[D] 1 joule = 1 Nm
Show Answer
Correct Answer: B [1 kg-m = 1 joule]
Notes:Joule is the absolute unit of work in S.I 1 joule = 1 Nm
- 1 joule= 107 ergs (erg is the unit of work in c.g.s)
- 1 erg = 1 dyne cm
- Also, Kilogram-metre (kg-m) is the gravitational unit of work on S.I 1 kg-m = 9.8 j
8. 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.
9. What is the difference of pressure between two sides of the liquid surface called as?
[A] Excess Pressure
[B] Surface Pressure
[C] Fluidic Tension
[D] Viscosity
Show Answer
Correct Answer: A [Excess Pressure]
Notes:
In equilibrium the pressure inside a bubble or drop is more than the pressure outside. The difference of pressure between two sides of the liquid surface is called as excess pressure.
10. What is Specific Gravity of a liquid?
[A] ratio of the density of a liquid to the density of water
[B] product of the density of a substance to the density of water
[C] ratio of the density of water to the density of a liquid
[D] ratio of density of the liquid to the mass of the equal density of water
Show Answer
Correct Answer: A [ ratio of the density of a liquid to the density of water ]
Notes:
Specific gravity of a liquid is the ratio of the density of a substance to the density of water. The density of liquid water at standard conditions on earth is approximately 1,000 kg/m3.
