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Question: Answered & Verified by Expert
A pendulum has an angular amplitude θ. The tension in the string at extreme position is T1 and at the bottom is T2. If it is known that T2 = 2T1, then what is the value of cosθ?
PhysicsLaws of MotionJEE Main
Solution:
2921 Upvotes Verified Answer
The correct answer is: 0.75
T 1 = mg cos θ        ..... (1)

T 2 - mg = mv 2 l = m l 2 gh

              = 2 mg l 1 - cos θ l

              = 2 mg 1 - cos θ l

or    T 2 = mg + 2 mg 1 - cos θ     ....... (2)



Given T2 = 2T1

or   mg + 2 mg 1 - cos θ = 2mg cos θ

or   cos θ = 3 4
                = 0.75

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