Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Speed is a scalar quantity.
Reason (R): A vector quantity is one that has both magnitude and direction.
In the light of the above two statements, choose the most appropriate answer from the options given below:
- A(A) is correct, but (R) is not correct
- BBoth (A) and (R) are incorrect
- CBoth (A) and (R) are correct and (R) is the correct explanation of (A)
- D(A) is not correct, but (R) is correct
Show answer and explanation
Correct answer: (c) Both (A) and (R) are correct and (R) is the correct explanation of (A)
Explanation
Both statements are correct, and (R) explains (A).
A vector quantity has both magnitude and direction and adds by the triangle (or parallelogram) law: for example, velocity, displacement, force and acceleration. A scalar has only magnitude: for example, speed, distance, mass, time and energy.
Speed tells only how fast a body moves, not in which direction, so it does not meet the condition in (R). It is therefore a scalar. Velocity, which also gives the direction, is its vector counterpart.