JEE Main Physics question

Physics Motion in a Straight Line JEE Main

Which of the following statements is true for a moving body?

(A)If its velocity changes, its speed must change and it must have some acceleration
(B)If its speed changes, its velocity may or may not change, and it must have some acceleration
(C)If its speed changes but the direction of motion does not change, its velocity may remain constant
(D)If its speed changes, its velocity must change and it must have some accelerationCorrect

Answer: (D)

Solution

(A) is false — velocity can change in direction alone (e.g. uniform circular motion) while speed stays constant. (B) is false — if speed (the magnitude of velocity) changes, the velocity vector has necessarily changed too, so "may or may not change" is incorrect; it must change. (C) is false — velocity is speed

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Question ID VK-152134