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.
31. Why is it easier to cook in a pressure cooker?
[A] High pressure creates turbulence
[B] More steam is formed inside the cooker
[C] Boiling point of water is raised
[D] Boiling point of water is lowered
Show Answer
Correct Answer: C [Boiling point of water is raised]
Notes:
When heat is supplied to the pressure cooker, after boiling point of liquid, pressure rises tremendously which raises boiling point temperature. This is due to steam trapped within the system and unable to escape from it. Hence pressure rises above atmospheric pressure.
32. What will happen to the portion of ship under water, when it enters a sea from a river?
[A] It will increase
[B] It will decrease
[C] It will show no change
[D] it will increase and decrease alternately
Show Answer
Correct Answer: B [It will decrease]
Notes:
When the ship enters the sea, the water is no more the river fresh water but the saline sea water which is denser. As a result the weight of water displaced is now more than what it was previously when the ship was in river. The upthrust increases and the ship rise up.
33. Which of the following has the similar properties to the Photons?
[A] Waves
[B] Particles
[C] Both particles and waves
[D] Neither particles nor waves
Show Answer
Correct Answer: B [Particles]
Notes:
To put it simply photons are the fundamental particle of light. They have a unique property in that they are both a particle and a wave. This is what allows photons unique properties like refraction and diffusion. However light particles are not quite the same as other elementary particles.
34. Which of the following is the minimum possible temperature beyond which matter cannot be cooled?
[A] -98.10° C
[B] -100.00° C
[C] -273.15° C
[D] -459.40° C
Show Answer
Correct Answer: C [-273.15° C]
Notes:
At the physically impossible-to-reach temperature of zero kelvin, or minus 459.67 degrees Fahrenheit (minus 273.15 degrees Celsius), atoms would stop moving. As such, nothing can be colder than absolute zero on the Kelvin scale.
35. Which of the following is the normal temperature of human body on the Kelvin scale?
[A] 280
[B] 290
[C] 300
[D] 310
Show Answer
Correct Answer: D [310]
Notes:
Normal body temperature of human is 37° C. But when we convert 37° C into Kelvin it becomes 310 K because 0° C = 0°C + 273 = 273 K.
36. In the Earth, the weight of a body is maximum at the__:
[A] Poles
[B] Equator
[C] Tropics of Cancer and Capricorn
[D] Centre of Earth
Show Answer
Correct Answer: A [Poles ]
Notes:
If the mass of the body is m, the force of attraction of the earth, or the weight w of the body, is given by the Newton’s law of gravitation as w = mg, with acceleration due to gravity g = GM R2 where M and R are the mass and radius of the Earth respectively. Since weight of the body is directly proportional to g, the weight of the body is maximum at poles and zero at the centre of the earth.
37. The passengers tends to lean forward When a running car stops suddenly because of__?
[A] centrifugal force
[B] inertia of rest
[C] inertia of motion
[D] gravitational force
Show Answer
Correct Answer: C [inertia of motion]
Notes:
When a running car stops suddenly, the passengers tend to lean forward due to inertia of motion. On applying brakes, the bus does stop but the passengers sitting in car remain in motion hence, as bus suddenly stop, they tend to continue in motion or going forward. Inertia is that property of a body due to which it resists a change in its state of rest or uniform motion.
38. The moment of inertia of a body does not depend upon which of the following?
[A] axis of rotation
[B] angular velocity
[C] form of mass
[D] distribution of mass
Show Answer
Correct Answer: B [angular velocity]
Notes:
Moment of inertia is the mass property of a rigid body that determines the torque needed for a desired angular acceleration about an axis of rotation. Moment of inertia depends on the shape of the body and the amount and distribution of its mass. It can be found through the sum of moments of inertia of the masses making up the whole object, under the same conditions.
39. Which of the following happens when a body moves with a constant speed in a circle?
[A] no work is done on it
[B] no force acts on it
[C] no acceleration is produced in it
[D] its velocity remains constant
Show Answer
Correct Answer: D [its velocity remains constant]
Notes:
A body moving with a constant speed in a circle is an example of uniform circular motion. The velocity vector is constant in magnitude but changing in direction. Since, velocity is a vector quantity that has both magnitude and direction, a change in either the magnitude or the direction constitutes a change in the velocity which leads to change in acceleration.
40. Which of the following is not a vector quantity?
[A] Momentum
[B] Displacement
[C] Torque
[D] Speed
Show Answer
Correct Answer: D [Speed]
Notes:
Speed is a scalar quantity that measures the rate at which an object changes its position. It refers only to how fast an object is moving, without any information about the direction. On the other hand, momentum, displacement, and torque are all vector quantities. They require both a magnitude and direction to fully describe them. Therefore, out of the options, speed is the one that is not a vector quantity.
