Work, Power and Energy: Roller Coaster MCQ

Solve this quality-checked JEE multiple-choice question, then review the correct answer and explanation.

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Roller CoasterHardQuestion 30441

Question

A ball starts from rest at height 20 m. What is the minimum height of the top of a loop (radius 5 m) to complete the loop without losing contact? (g = 10)

A
12.5 m
Correct
B
10 m
C
15 m
D
5 m

Correct answer

12.5 m

Explanation

At the top of the loop: minimum speed v_top = √(gR). Energy: mgh = mg(2R) + ½mv_top² = mg(2R) + ½mgR = mg(5R/2). h = 5R/2 = 12.5 m.

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