Physics
Assertion (A) : The displacement of a body can be zero even if the distance travelled by it is not zero.
Reason (R) : Displacement is the shortest distance from the initial to the final position of body.
- both A and R are true and R is the correct explanation of A
- both A and R are true and R is not the correct explanation of A
- assertion is false but reason is true
- assertion is true but reason is false
Motion in One Dimension
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Answer
both A and R are true and R is the correct explanation of A
Explanation
Assertion (A) is true because if a body moves and comes back to its starting point (e.g., in a circular path or a round trip), the displacement is zero because the initial and final positions are the same, but the distance travelled is not zero.
Reason (R) is true because by definition, displacement is the shortest straight line distance between the initial and final positions of the body. So, the reason correctly explains the assertion.
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Related Questions
A space craft flying in a straight course with a velocity of 75 km s-1 fires its rocket motors for 6.0 s. At the end of this time, its speed is 120 km s-1 in the same direction.
Find —
(i) the space craft’s average acceleration while the motors were firing
(ii) the distance travelled by the space craft in the first 10 s after the rocket motors were started, the motors having been in action for only 6.0 s.
A train starts from rest and accelerates uniformly at a rate of 2 m s-2 for 10 s. It then maintains a constant speed for 200 s. The brakes are then applied and the train is uniformly retarded and comes to rest in 50 s.
Find —
(i) the maximum velocity reached,
(ii) the retardation in the last 50 s,
(iii) the total distance travelled, and
(iv)the average velocity of the train.
Assertion (A) : For a given time interval, average velocity and average speed can have different values.
Reason (R) : Speed is a scalar quantity whereas velocity is a vector quantity.
- both A and R are true and R is the correct explanation of A
- both A and R are true and R is not the correct explanation of A
- assertion is false but reason is true
- assertion is true but reason is false
Assertion (A) : The slope of displacement-time graph gives the velocity.
Reason (R) : Velocity is the product of displacement and time.
- both A and R are true and R is the correct explanation of A
- both A and R are true and R is not the correct explanation of A
- assertion is false but reason is true
- assertion is true but reason is false