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. Which of the following term denotes the internal reaction force per unit area developed as a result of applied external force ?
[A] Stress
[B] Friction
[C] Moment of Inertia
[D] tension
Show Answer
Correct Answer: A [Stress]
Notes:
Stress is the force acting per unit area. It is the internal force reaction per unit area developed as a result of external force.
2. Which among the following sentence is correct reason behind the blue color of ocean water?
[A] Water molecules absorb all other colors except blue
[B] Impurities in Sea water reflect the blue light
[C] Water molecules scatter the blue light
[D] None of the above
Show Answer
Correct Answer: C [Water molecules scatter the blue light]
Notes:
Water molecules scatter the blue light by absorbing the light waves and then rapidly re-emitting the light waves in different directions. That is why there are mostly blue wavelengths that are reflected back to our eyes.
3. What happens when a ship enters a Sea from a river ?
[A] It rises
[B] It remains at the same level
[C] sinks a little
[D] None of the above
Show Answer
Correct Answer: A [It rises]
Notes:
When a ship enters a sea from a river ,the ship is elevated or uplifted due to the density of sea water and during the buoyant motion of the ship, as it would gain both potential and kinetic energy when rising in the fluid.
4. On which of the following the jet Engine works?
[A] Conservation of energy
[B] Conservation of Linear Momentum
[C] Conservation of Mass
[D] Conservation of Angular momentum
Show Answer
Correct Answer: B [Conservation of Linear Momentum]
Notes:Conservation of Linear Momentum law says that if no external force acts on a system, then its total linear momentum remains conserved. In equation form, Momentum=mass*velocity. To increase the momentum of an object, we need to either increase its mass or velocity or both.
- Rockets work on law of conservation of momentum. As momentum in one direction is given to the rocket’s exhaust gases, momentum in the other direction is given to the rocket itself.
5. 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.
6. In which of the following conditions, a Balloon filled with a gas such as Hydrogen will tend to rise up?
[A] If the buoyant force exerted by the air on a balloon is greater than the weight of the balloon
[B] If the buoyant force exerted by the air on a balloon is less than the weight of the balloon
[C] If the buoyant force exerted by the air on a balloon is equal to the weight of the balloon
[D] If the density of the air is greater than the density of the gas filled in balloon
Show Answer
Correct Answer: A [ If the buoyant force exerted by the air on a balloon is greater than the weight of the balloon]
Notes:
A Balloon filled with a gas such as Hydrogen gas is much lighter in weight than the weight of air displaced by it. So the buoyant force exerted by the air on a balloon is greater than the weight of the balloon. The hydrogen gas which is lighter than air enables the balloon to float.
7. In which among the following, the speed of sound would be maximum?
[A] Dry air at 0°C
[B] Dry air at 30°C
[C] Humid air at 0°C
[D] Humid air at 30°C
Show Answer
Correct Answer: D [ Humid air at 30°C]
Notes:
The speed of sound in a medium depends on temperature of the medium. The speed of sound decreases when we go from solid to gaseous state. In any medium as we increase the temperature the speed of sound increases.. The speed of sound will be highest in humid air at 30°C.
8. Who among the following is credited for the discovery of ‘Expanding Universe’?
[A] Edwin Hubble
[B] Niels Bohr
[C] S Chandra Shekhar
[D] C.V Raman
Show Answer
Correct Answer: A [Edwin Hubble]
Notes:
Edwin Hubble, an american astronomer, and was the first to prove that the universe is expanding. According to Expanding Universe theory, the universe is presently expanding. Hubble proved that there is a direct relationship between the speeds of distant galaxies and their distances from Earth. This is now known as Hubble’s Law.
9. Which of the following physical quantities has no units?
[A] Reynold Number
[B] Rydberg constant
[C] Wave number
[D] Hubble constant
Show Answer
Correct Answer: A [ Reynold Number ]
Notes:Reynold Number has no units. The Reynolds number is the ratio of inertial forces to viscous forces. It is used for predicting if a flow condition will be laminar or turbulent.
- Unit of Rydberg constant: m-1
- Unit of Wave number = m-1
- Unit of Hubble constant = sec-1
10. The branch of mechanics which deals with the study of motion of material objects without taking into account the factors which cause motion is called as:
[A] Statics
[B] Kinematics
[C] Dynamics
[D] None of the above
Show Answer
Correct Answer: B [Kinematics]
Notes:
The branch of mechanics which deals with the study of motion of material objects without taking into account the factors which cause motion is called as Kinematics. The branch of mechanics which deals with the study of motion of material objects taking into account the factors which cause motion is called as Dynamics. The branch of mechanics which deals with the study of material objects at rest is called as Statics.
