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Science Assertion (A) & Reason (B) MCQ

Motion · Rajasthan Board (RBSE) STD 9 (Rajasthan - English Medium). 6 questions.

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Assertion (A) & Reason (B) MCQ

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Question 11 Mark
In the following Questions, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following:
  1. Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
  2. The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
  3. Assertion is true but the Reason is false.
  4. The statement of the Assertion is false but the Reason is true.
Assertion: Equations of motion can when the acceleration is $a = 2t$ where $t$ seconds.
Reason: The slope of a $v-t$ graph with $60^\circ$ inclination is greater than $30^\circ$ inclination.
Answer
The slope of the distance$–$time graph gives the speed of the object.For the particale $A$, the slope of the line is $\tan\theta_1=\tan30=\frac{1}{\sqrt{3}}$
For the particale $B,$ the slope of the line is $\tan\theta_2=\tan60=\sqrt{3}$
Thus, ratio of the velocities, $\frac{\text{V}_{\text{A}}}{\text{V}_{\text{B}}}=\frac{\tan30}{\tan60}=\frac{\frac{1}{\sqrt{3}}}{\sqrt{3}}=\frac{1}3{}$
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Question 21 Mark
In the following questions, a statement of Assertion is given by the corresponding statement of Reason. Of the statements, mark the correct answer as:
  1. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
  2. If both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
  3. If Assertion is true, but Reason is false.
  4. If Assertion is false, but Reason is true.
  5. If Assertion and Reason both are false.
Assertion: A body performing uniform circular motion with constant speed may have acceleration.
Reason: When speed of a body remains constant, then its acceleration is always zero.
Answer
  1. If Assertion is true, but Reason is false.
Explanation:
If the speed remains constant, then the component of acceleration which is parallel to the velocity is zero. This component is called as tangential acceleration. The direction changes due to the centripetal acceleration which is radially inward.
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Question 31 Mark
In the following questions, a statement of Assertion is given by the corresponding statement of Reason. Of the statements, mark the correct answer as:
  1. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
  2. If both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
  3. If Assertion is true, but Reason is false.
  4. If Assertion is false, but Reason is true.
  5. If Assertion and Reason both are false.
Assertion: Acceleration of a body can be calculated from velocity-time graph.
Reason: Area of velocity-time graph gives distance travelled by the body.
Answer
  1. If both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
Explanation:
A velocity vs time graph shows the velocity change with respect to time.
Acceleration is defined exactly as the rate of change of velocity with respect to time.
$\text{a}=\frac{\text{dv}}{\text{dt}}$
Basically what I’m trying to say here is: divide the change in velocity by the change of time and you’ll get the slope of something (a something that is a line if the motion is uniformly accelerated), which is defined as the acceleration.
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Question 41 Mark
In the following questions, a statement of Assertion is given by the corresponding statement of Reason. Of the statements, mark the correct answer as:
  1. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
  2. If both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
  3. If Assertion is true, but Reason is false.
  4. If Assertion is false, but Reason is true.
  5. If Assertion and Reason both are false.
Assertion: Distance travelled by a body may be positive, negative or zero.
Reason: Shortest distance travelled by the body between two points is called distance.
Answer
  1. If Assertion is false, but Reason is true.
Explanation:
Displacement is the shortest distance travelled by the object. it can be positive when object moves in the straight line. it cannot be negative. it can be zero when initial and final position is same.
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Question 51 Mark
In the following Questions, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following:
  1. Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
  2. The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
  3. Assertion is true but the Reason is false.
  4. The statement of the Assertion is false but the Reason is true.
Assertion: Newton's equations of motion hold true for uniformly accelerated motion only.
Reason: The equations of motion do not apply to freely falling body as its motion is not uniformly accelerated.
Answer
  1. Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
Explanation:
In case of uniform acceleration, there are three equations of motion which are also known as the laws of constant acceleration. Hence, these equations are used to derive the components like displacement(s), velocity (initial and final), time(t) and acceleration(a).
Freely falling body experiences constant accelaration due to gravity, hence the motion is said to be accelarated. The acceleration is said to be uniform, if equal changes in velocity take place in equal intervals of time. The motion of body under gravity is an example of uniformly accelerated motion.
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Question 61 Mark
In the following Questions, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following:
  1. Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
  2. The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
  3. Assertion is true but the Reason is false.
  4. The statement of the Assertion is false but the Reason is true.
Assertion: The slope of distance time graph gives acceleration of the body.
Reason: Greater the slope of distance time graph, more is the speed of the body.
Answer
  1. Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
Explanation:
The slope on a velocity-time graph represents the acceleration of an object. The distance travelled is equal to the area under a velocity-time graph. It depicts the acceleration of a moving body with respect to the distance it covers in a particular amount of time.
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Assertion (A) & Reason (B) MCQ - Science STD 9 Questions - Vidyadip