(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 4 kg block, 10m above the ground is attached to a long cord which is wrapped around a 1050 g iron disc of radius 40 cm. The system is originally at rest, afterwards the block is let go and allowed to fall. From the time the block is let go to when the block crashes with the ground, calculate the speed of the block as it hits the ground

the number of revolutions the disc makes

2. Relevant equations

energy equations

3. The attempt at a solution

For the linear speed as it hits the ground i used

mgh = .5m1v^{2}+ .5Iω^{2}

Where I = 1.050*.4^{2}*.5

m1 is the mass of the disc + the block, so 1.050+5kg = 5.050 kg

I replaced ω with v/r, to have the equation

mgh = .5mv^{2}+ .5I(v/r)^{2}

Is this correct?

For the revolutions, I would probably use

θ = ωt + .5αt^{2}, where t = (ωf - ωi)/α

is this part correct?

Thanks

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# Homework Help: Rotational Speed/Linear Speed help, need confirmation

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