General Science - Physics
Welcome to General Science – Physics MCQ series of GKToday. As of today February 27, 2020, this series has 590 Questions. You may purchase a PDF E-Book compilation comprising all these questions and their answers with explanation from this link.
11. Light year is a unit of which of these following?
[A] distance
[B] time
[C] pressure
[D] power
Show Answer
Correct Answer: A [ distance ]
Notes:
Light year is a unit of distance. One light year is the distance travelled by light in vacuum in one year. 1 light year = 9.46 x 1015 m velocity of light in vacuum = 3 x108 m/s
12. Which of these pairs has the same unit of measurement?
[A] Rate of flow and Acceleration
[B] Impulse and Moment of Force
[C] Rydberg constant and Gas constant
[D] Pressure and Coefficient of Elasticity
Show Answer
Correct Answer: D [ Pressure and Coefficient of Elasticity ]
Notes:
Pressure and Coefficient of Elasticity have the same unit i.e. N m-2 (Newton per metre square) Other important units: Rate of Flow: m3s-1 Acceleration: ms-2 Rydberg constant: 1/m Gas constant: J/K Impulse: Ns Moment of Force: Nm
13. Which of the following is true about displacement of an object?
[A] It is always equal to the distance travelled by the object
[B] It can be less than the distance travelled by the object
[C] It can be greater than the distance travelled by the object
[D] It always less than the distance travelled by the object
Show Answer
Correct Answer: B [It can be less than the distance travelled by the object]
Notes:
The displacement is the shortest distance between the initial and final position of an object in the given time. The displacement of an object is a vector quantity. It can be less than or equal to the distance but can never be greater than the distance travelled by that object
14. 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.
15. Which of the following are Polar vectors?
[A] Displacement
[B] Force
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
The polar vectors are those vectors which have a starting point or a point of application. Examples of Polar vector: Force, Displacement etc. Those vectors which represent rotational effect are called as axial vectors. Example: Angular velocity, Torque, Angular Momentum etc.
16. Which of the following is correct about Kinetic energy during the projectile motion?
[A] it is minimum at the point of projection
[B] it is minimum at the highest point
[C] it is maximum at the highest point
[D] it is minimum at the point of reaching the ground
Show Answer
Correct Answer: B [it is minimum at the highest point]
Notes:
The Kinetic energy of an object is maximum at the point of projection or at the point of reaching the ground. It is minimum at the highest point.
17. What is the relationship between Kinetic and limiting friction?
[A] Kinetic friction is slightly greater than limiting friction
[B] Kinetic friction is slightly less than limiting friction
[C] Kinetic friction is equal to limiting friction
[D] No relationship
Show Answer
Correct Answer: B [Kinetic friction is slightly less than limiting friction]
Notes:
The Kinetic friction is always slightly less than the limiting friction. This is because once the motion has started, the inertia of has been overcome and irregularities of one surface have little or no time to get locked into the irregularities of the other surface.
18. Which of the following is NOT correct about the velocity of rocket at any time?
[A] it is directly proportional to the exhaust speed of the gases
[B] it is directly proportional to the natural log of ratio of intial mass of rocket to its mass at that instant
[C] length of the rocket
[D] All of the above
Show Answer
Correct Answer: C [length of the rocket]
Notes:
The velocity of rocket at any time is directly proportional to the exhaust speed of the gases and to the natural log of ratio of intial mass of rocket to its mass at that instant. V = u log(m1/m2)
19. As per the Newton’s second law of motion, what is the relation between the rate of change of linear momentum and the external force applied?
[A] directly proportional
[B] inversely proportional
[C] independent of each other
[D] None of the above
Show Answer
Correct Answer: B [inversely proportional]
Notes:
As per the Newton’s second law of motion, the rate of change of linear momentum of a body is inversely proportional to the external force applied on the body. This change always takes place in the direction of the force applied.
20. Work done is defined as the dot product of which of the following vectors?
[A] Force and acceleration
[B] Force and area
[C] Force and instantaneous velocity
[D] Force and displacement
Show Answer
Correct Answer: D [Force and displacement]
Notes:
Work done is defined as the dot product of Force vector and displacement vector. W = F.s Work done is a scalar quantity. Note: Instantaneous power is defined as the dot product of Force vector and instantaneous velocity.
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