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. What is the focal length of a concave lense with number -5D?
[A] 5 cm
[B] 10 cm
[C] 15 cm
[D] 20 cm
Show Answer
Correct Answer: D [20 cm]
Notes:
A concave lens is a type of lens that has a thinner center than edges, and it is sometimes called a diverging lens because it spreads out light rays that are parallel to its axis. The focal length of a lens is a measure of its ability to focus light, and it is defined as the distance from the lens to the point where the light rays converge. In the case of a concave lens with a power of -5D, the focal length would be equal to 1/5 of a meter, or 20 centimeters.
2. A pendulum is taken to Moon, what will happen to its time period?
[A] Increases
[B] Decreases
[C] Remains constant
[D] Either increase or decrease
Show Answer
Correct Answer: A [Increases]
Notes:
When the simple pendulum is taken to the moon, value of gravitational constant g will decrease and thus, its time period will increase.
3. The speed of Sound is maximum in which of the following ?
[A] Air at zero degree C
[B] Air at 100 degree C
[C] Water
[D] Same in all
Show Answer
Correct Answer: C [Water]
Notes:The speed of sound in a medium is determined by the properties of that medium, primarily its density and elasticity. The speed of sound is fastest in solids, followed by liquids, and then gases. Let’s analyze the given options:
[A] Air at zero degrees Celsius: The speed of sound in air increases with temperature. At lower temperatures, the molecules in the air have less kinetic energy, which results in a slower speed of sound. So, the speed of sound in air at 0°C is slower compared to higher temperatures.
[B] Air at 100 degrees Celsius: As mentioned earlier, the speed of sound in air increases with temperature. So, the speed of sound in air at 100°C would be faster than at 0°C but still slower than in a solid or liquid.
[C] Water: The speed of sound in water is significantly faster than in air. Water is denser and more elastic than air, which allows sound waves to travel through it more quickly.
[D] same in all: This statement is not correct. The speed of sound varies depending on the medium. It is not constant and is definitely not maximum everywhere.
So, among the given options, the maximum speed of sound would be in “Water” (Option C).
4. On which of the following Inertia of an object depends ?
[A] Bulk
[B] Size
[C] Shape
[D] Mass
Show Answer
Correct Answer: D [Mass]
Notes:
Inertia is the resistance experienced by an object to any change in its velocity. This includes changes to the object’s speed, or direction of motion. Inertia of rest, Inertia of motion are the examples.
5. The term “Isopycnic” is most closely defined by which among the following?
[A] Two places with same atmospheric pressure
[B] Two liquids with same viscosity
[C] Two liquids with same density
[D] Two places with same temperature
Show Answer
Correct Answer: C [Two liquids with same density]
Notes:
The term “Isopycnic” refers to two substances having the same density. It is derived from the Greek words “iso,” meaning equal, and “pycnos,” meaning dense. In scientific contexts, isopycnic conditions are often used in centrifugation techniques to separate particles based on their density, such as in the purification of DNA or proteins.
6. If the distance between the earth and the sun becomes one-fourth of what it is now, the gravitational force exerted on the earth by the sun would be:
[A] One-fourth of what it is now
[B] One-sixteenth of what it is now
[C] Sixteen times of what it is now
[D] Four times of what it is now
Show Answer
Correct Answer: C [ Sixteen times of what it is now]
Notes:
Gravitational force is inversely proportional to the square of the distance between the bodies.
7. A cardboard is placed on a glass of water, and a ten paise coin is placed on the cardboard. If the cardboard is flicked suddenly in the direction parallel to its surface, then the cardboard flies away, but the coin falls in the glass.
The behaviour of the coin can be explained by which among the following properties?
[A] Momentum
[B] Acceleration
[C] Inertia
[D] Friction
Show Answer
Correct Answer: C [ Inertia]
Notes:
Inertia is the property of matter that is why it continues in its existing state of either rest or motion. It can be changed by an external force. Here in the question the coin falls in the glass even after the cardboard is flicked because it maintains its rest position by the nature of inertia.
8. You are sitting inside an open vehicle moving with uniform speed. When you throw a stone vertically upwards, the stone will fall__:
[A] Ahead of you
[B] Behind you
[C] Over you
[D] Either ahead or behind of you
Show Answer
Correct Answer: C [ Over you]
Notes:
Uniform speed means no acceleration. If there is no acceleration and the vehicle is moving with uniform speed; the stone will fall over you.
9. Which of the following branch of Physics deal with study of Atomic Nuclei?
[A] Nuclear Physics
[B] Bio Physics
[C] Atomic Physics
[D] None of the above
Show Answer
Correct Answer: A [Nuclear Physics]
Notes:
Nuclear physics is a branch of physics that deals with the constituents, structure, behaviour and interactions of atomic nuclei. Atomic physics is a branch of physics that deals with the composition of the atom apart from the nucleus
10. Which of the following is the unit of Impulse?
[A] N
[B] Ns
[C] N/s
[D] Ns2
Show Answer
Correct Answer: B [ Ns ]
Notes:
The unit of impulse is Ns. Impulse = Force(N) x Time(s) Impulse can be defined as the integral of a force, F, over the time interval, t, for which it acts.
