Given that the mass of the string m = 4.2 Kg
The length of the string is L = 3.8 m
At the lowest point the velocity is U = 9.3 m/s
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The angle is θ1 = 540
apply conservation at the lowest point and an angle θ1 is
(1/2)mU2 + 0 = mgh + (1/2) mV2
U2 = 2gL(1-cosθ1) + V2
V = ( U
2 - 2gL(1-cosθ1) )
1/2
= ------------- m/s
where V is the velocity of the body at the an angle θ1
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From the conservation of energy the maximum angle reached by the body is
(1/2)mU
2 + 0 = mgh
U2 = 2gL(1-cosθ)
cosθ =1 - ( U2 / 2gL)
then we get the angle is θ = ---------- degrees
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The total mechanical energy of the system is T.E = (1/2)mU2 + 0
= (1/2)mU2
= ---------J
since the potential energy at the lowest point is 0 so the toatal mechanical energy is equal to the kinetic energy at the
lowest point .