JEE  >  Assertion-Reason Type Questions: Motion

# Assertion-Reason Type Questions: Motion | All Types of Questions for JEE

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Directions : Each of these questions contain two statements, Assertion and Reason. Each of these questions also has alternative choices, only one of which is the correct answer.
Q.1. Assertion : A body may be accelerated even when it is moving uniformly.
Reason : When direction of motion of the body is changing, the body must have acceleration.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (a)
In uniform circular motion, there is acceleration of constant magnitude.

Q.2. Assertion : Displacement of a body may be zero when distance travelled by it is not zero.
Reason : The displacement is the longest distance between initial and final position.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (c)
The displacement is the shortest distance between initial and final position. When final position of a body coincides with its initial position, displacement is zero, but the distance travelled is not zero.

Q.3. Assertion : For one dimensional motion the angle between acceleration and velocity must be zero.
Reason : One dimensional motion is always on a straight line.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (d)
One dimensional motion is always along straight line. But acceleration may be opposite of velocity and so angle between them will be 180°.

Q.4. Assertion : Displacement of a body is vector sum of the area under velocity– time graph.
Reason : Displacement is a vector quantity.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (a)
According to definition, displacement = velocity × time. Since displacement is a vector quantity so its value is equal to the vector sum of the area under velocity-time graph.

Q.5. Assertion : Position-time graph of a stationary object is a straight line parallel to time axis.
Reason : For a stationary object, position does not change with time.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (a)
Position-time graph for a stationary object is a straight line parallel to time axis showing that not change in position with time.

Q.6. Assertion : Velocity-time graph for an object in uniform motion along a straight path is a straight line parallel to the time axis.
Reason : In uniform motion of an object velocity increases as the square of time elapsed.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (c)
In uniform motion the object moves with uniform velocity, the magnitude of its velocity at different instance i.e., at t = 0, t =1, sec, t = 2sec ….. will always be constant. Thus velocity-time graph for an object in uniform motion along a straight path is a straight line parallel to time axis.

Q.7. Assertion : The average and instantaneous velocities have same value in a uniform motion.
Reason : In uniform motion, the velocity of an object increases uniformly.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (c)
In uniform motion the speed is same at each instant of motion.

Q.8. Assertion: The average velocity of the object over an interval of time is either smaller than or equal to the average speed of the object over the same interval.
Reason: Velocity is a vector quantity and speed is a scalar quantity.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (a)
Because displacement ≤ distance and so average velocity ≤ average speed.

Q.9. Assertion : The speedometer of an automobile measure the average speed of the automobile.
Reason : Average velocity is equal to total displacement per total time taken.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (d)
Speedometer measures instantaneous speed of automobile.

Q.10. Assertion : An object can have constant speed but variable velocity.
Reason : Speed is a scalar but velocity is a vector quantity.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (a)
Since velocity is a vector quantity, hence as its direction changes keeping magnitude constant, velocity is said to be changed. But for constant speed in equal time interval distance travelled should be equal.

Q.11.  Assertion : position-time graph of a body moving uniformly in a straight line parallel to position axis. Says body is at rest.
Reason : The slope of position-time graph in a uniform motion gives the velocity of an object.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (c)
If the position-time graph of a body moving uniformly in a straight line parallel to position axis, it means that the position of body is changing at constant time. The statement is abrupt and shows that the velocity of body is infinite.

Q.12. Assertion : The position-time graph of a uniform motion in one dimension of a body can have negative slope.
Reason : When the speed of body decreases with time, the position-time graph of the moving body has negative slope.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Correct Answer is option (c)
Negative slope of position time graph represents that the body is moving towards the negative direction and if the slope of the graph decrease with time then it represents the decrease in speed i.e. retardation in motion.

Q.13. Assertion: A body can have acceleration even if its velocity is zero at a given instant of time.
Reason: A body is momentarily at rest when it reverses its direction of motion.
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) If assertion is true but reason is false.
(d) If the assertion and reason both are false.
(e) If assertion is false but reason is true.

Correct Answer is option (a)
When body going vertically upwards, reaches at the highest point, then it is momentarily at rest and it then reverses its direction. At the highest point of motion, its velocity is zero but its acceleration is equal to acceleration due to gravity.

Q.14. Assertion: Two balls of different masses are thrown vertically upward with same speed. They will pass through their point of projection in the downward direction with the same speed.
Reason: The maximum height and downward velocity attained at the point of projection are independent of the mass of the ball.
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) If assertion is true but reason is false.
(d) If the assertion and reason both are false.
(e) If assertion is false but reason is true.

Correct Answer is option (a)
As motion is governed by force of gravity and acceleration due to gravity (g) is independent of mass of object.

Q.15.  Assertion: If the displacement of the body is zero, the distance covered by it may not be zero.
Reason: Displacement is a vector quantity and distance is a scalar quantity.
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) If assertion is true but reason is false.
(d) If the assertion and reason both are false.
(e) If assertion is false but reason is true.

Correct Answer is option (a)
As distance being a scalar quantity is always positive but displacement being a vector may be positive, zero and negative depending on situation.

Q.16. Assertion: The average velocity of the object over an interval of time is either smaller than or equal to the average speed of the object over the same interval.
Reason: Velocity is a vector quantity and speed is a scalar quantity.
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) If assertion is true but reason is false.
(d) If the assertion and reason both are false.
(e) If assertion is false but reason is true.

Correct Answer is option (a)
As displacement is either smaller or equal to distance but never be greater than distance.

Q.17. Assertion: An object can have constant speed but variable velocity.
Reason: Speed is a scalar but velocity is a vector quantity.
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) If assertion is true but reason is false.
(d) If the assertion and reason both are false.
(e) If assertion is false but reason is true.

Correct Answer is option (a)
Since velocity is a vector quantity, hence as its direction changes keeping magnitude constant, velocity is said to be changed. But for constant speed in equal time interval distance travelled should be equal.

Q.18. Assertion: The speed of a body can be negative.
Reason: If the body is moving in the opposite direction of positive motion, then its speed is negative.
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) If assertion is true but reason is false.
(d) If the assertion and reason both are false.
(e) If assertion is false but reason is true.

Correct Answer is option (d)
Speed can never be negative because it is a scalar quantity.

Q.19. Assertion: The position-time graph of a uniform motion in one dimension of a body can have negative slope.
Reason: When the speed of body decreases with time, the position-time graph of the moving body has negative slope.
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) If assertion is true but reason is false.
(d) If the assertion and reason both are false.
(e) If assertion is false but reason is true.

Correct Answer is option (c)
Negative slope of position time graph represents that the body is moving towards the negative direction and if the slope of the graph decrease with time then it represents the decrease in speed i.e. retardation in motion.

Q.20. Assertion: A positive acceleration of a body can be associated with a slowing down of the body.
Reason: Acceleration is a vector quantity.
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) If assertion is true but reason is false.
(d) If the assertion and reason both are false.
(e) If assertion is false but reason is true.

Correct Answer is option (b)
A body having positive acceleration can be associated with slowing down, as time rate of change of velocity decreases, but velocity increases with time, from graph it is clear that slope with time axis decreases, but velocity increases with time.

The document Assertion-Reason Type Questions: Motion | All Types of Questions for JEE is a part of the JEE Course All Types of Questions for JEE.
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