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ANEK [815]
3 years ago
8

This is may mastering physics homework and I just need help solving the question.

Physics
1 answer:
laila [671]3 years ago
6 0

Answer:

Angular speed of the disc after he fold his hands is given as

\omega_f = 27.5 rpm

Explanation:

As we know that the moment of inertia of the solid cylinder is given as

I_1 = \frac{m_1r_1^2}{2}

so we have

I_1 = \frac{(950/9.81)(0.20)^2}{2}

I_1 = 1.94 kg m^2

now moment of inertia of two dumbbell in his hand is given as

I_2 = 2(m_2 r_2^2)

I_2 = 2(4)(0.85)^2

I_2 = 5.78 kg m^2

Now moment of inertia of the disc is given as

I_3 = \frac{1}{2}MR^2

I_3 = \frac{1}{2}(1500/9.81)(2^2)

I_3 = 305.8 kg m^2

Now we can use angular momentum conservation as there is no external torque on it

(I_1 + I_2 + I_3) \omega_i = (I_1 + I_3)\omega_f

(1.94 + 5.78 + 305.8) 27 = (1.94 + 305.8) \omega_f

\omega_f = 27.5 rpm

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