MHT CET · Physics · Motion In Two Dimensions

A mass attached to one end of a string crosses topmost point on a vertical circle with critical speed. Its centripetal acceleration when string becomes horizontal will be ( $g =$ gravitational acceleration)

A $g$
B 3 $g$
C 4 $g$
D 6 $g$

Verified Solution

Answer & Solution

Correct Answer

(B) 3 $g$

Step-by-step Solution

Detailed explanation

Critical velocity at top most point

v = \sqrt{r g}

∴

Velocity when string become horizontal

v' = \sqrt{υ^{2} + 2 g r}

= \sqrt{3 g r}

Centripetal acceleration

= \frac{υ^{2}}{r} = \frac{3 r g}{r} = 3 g

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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A mass attached to one end of a string crosses topmost point on a vertical circle with critical speed. Its centripetal acceleration when string becomes horizontal will be ( g= gravitational acceleration)

Step-by-step Solution

A mass attached to one end of a string crosses topmost point on a vertical circle with critical speed. Its centripetal acceleration when string becomes horizontal will be ( $g =$ gravitational acceleration)