Laws of Motion - Result Question 62

62. A body of mass 0.4kg is whirled in a vertical circle making 2rev/sec. If the radius of the circle is 1.2m, then tension in the string when the body is at the top of the circle, is [1999]

(a) 41.56N

(b) 89.86N

(c) 109.86N

(d) 115.86N

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Answer:

Correct Answer: 62. (a)

Solution:

  1. (a) Given : Mass (m)=0.4kg Its frequency (n)=2rev/sec

Radius (r)=1.2m. We know that linear velocity of the body (v)=ωr=(2πn)r =2×3.14×2×1.2=15.08m/s.

Therefore, tension in the string when the body is at the top of the circle (T)

=mv2rmg=0.4×(15.08)22(0.4×9.8)=45.783.92=41.56N



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