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. When two mercury drops are brought into contact they form a single bigger drop to get which of the following?
[A] Minimum volume
[B] Minimum surface area
[C] Maximum size
[D] Maximum surface area
Show Answer
Correct Answer: B [Minimum surface area]
Notes:
When two drops of mercury come into contact, they will tend to merge together and form a single drop with a minimum surface area. This is because of the properties of mercury, which is a liquid metal with a high surface tension. The surface tension of a liquid is a measure of its elasticity, and it is determined by the cohesive forces between the molecules of the liquid. In the case of mercury, the high surface tension causes the molecules at the surface of the liquid to be strongly attracted to each other, which results in the formation of a relatively smooth and spherical surface. When two drops of mercury are brought together, the surface tension causes them to merge and form a single drop with the smallest possible surface area. This phenomenon is known as the “minimization of surface area” and it is a common feature of liquids with high surface tension.
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. In which of the following situations the force applied by the weight of a person becomes zero in a lift
[A] Lift moves up with an acceleration of 9.8 meter per sq. second
[B] Lift moves down with an acceleration of 9.8 meter per sq. second
[C] Lift moves up with an speed of 9.8 meter per second
[D] Lift moves up with down speed of 9.8 meter per second
Show Answer
Correct Answer: B [Lift moves down with an acceleration of 9.8 meter per sq. second]
Notes:
The weight of a person becomes zero in a lift. Lift moves down with an acceleration of 9.8 meter per sq. second.
6. Which of the following is an instrument for measuring electric charge or electrical potential difference?
[A] Ammeter
[B] Voltmeter
[C] Electrometer
[D] ohmmeter
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Correct Answer: B [Voltmeter]
Notes:
Voltmeter is an instrument for measuring electric charge or electrical potential difference. It was invented by Hans Christian Oersted.
7. 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
8. The forces acting at a point are called as:
[A] Collinear forces
[B] Coplanar forces
[C] Concurrent forces
[D] Unit forces
Show Answer
Correct Answer: C [Concurrent forces]
Notes:
The forces which are acting at a point are called as concurrent forces. Note: When concurrent forces in equilibrium act on a body, the state of the body shall remain unchanged i.e. if the body is at rest, it will continue to be at rest. Similarly, a body will continue to move uniformly along the same straight line, if concurrent forces in equilibrium are applied on the body.
9. Which of these is the force required to move a body uniformly in a circle?
[A] Centrifugal force
[B] Centripetal force
[C] Kinetic force
[D] None of the above
Show Answer
Correct Answer: B [Centripetal force]
Notes:
Centripetal force is the force required to move a body uniformly in a circle. This force acts along the radius and towards the centre of the circle. Centrifugal force is the force that arises when a body is moving actually along a circular path by virtue of the tendency of the body to regain its path.
10. The centripetal force and centrifugal force are ______:
[A] equal in magnitude and have same direction
[B] unequal in magnitude and have same direction
[C] equal in magnitude and have opposite direction
[D] unequal in magnitude and have opposite direction
Show Answer
Correct Answer: C [equal in magnitude and have opposite direction]
Notes:
The centripetal force and centrifugal force are equal in magnitude and have opposite direction. Centrifugal force can be regarded as the reaction of centripetal force.
