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

http://urlcut.com/katrolafbeelding.gif

What is the accelaration of a point on the circumference of the disk?

2. Relevant equations

[tex]\tau[/tex] = F.R = I.[tex]\alpha[/tex]

I = M.R²/2

a = R.[tex]\alpha[/tex]

F(z) = m.g

3. The attempt at a solution

The mass exerts a force F(z) = m.g on the disk. This force is what puts the disk into motion with [tex]\tau[/tex] = F(z).R = m.g.R (1)

Also, as I = M.R²/2 and a = R.[tex]\alpha[/tex] and [tex]\tau[/tex] = I.[tex]\alpha[/tex]

==> [tex]\tau[/tex] = M.R.a/2 (2)

Out of (1) & (2):

m.g.R = M.R.a/2 <=> m.g = M.a/2 <=> a = 2m.g/M

The acceleration asked for isa = 2m.g/M

But the teacher's solution says: [tex]\frac{2m.g}{2m+M}[/tex]

What have I done wrong?

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# Homework Help: What is the acceleration of a point on the circumference of the disk?

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