Q64 / 90 · JEE Main 2024 (29 Jan Shift 2) · Physics

A particle is moving in a circle of radius 50 cm in such a way that at any instant the normal and tangential components of its acceleration are equal. If its speed at t=0 is 4 m s-1, the time taken to complete the first revolution will be 1α1-e-2π s, where α=______.

Correct answer: 8

Solution

Given:

a→c=a→t

⇒v2r=dvdt

⇒∫4vdvv2=∫0tdtr

⇒-1v4v=tr

⇒-1v+14=2t

⇒v=41-8t=dsdt

⇒4∫0tdt1-8t=∫0sds

r=0.5 m, distance covered s=2πr=π

⇒4×[ln(1-8t)]0t-8=π

⇒ℓn(1-8t)=-2π

⇒1-8t=e-2π

⇒t=1-e-2π18 s

So, α=8.

Hence, the correct answer is 8.

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