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1. The problem statement, all variables and given/known data
This problem was originally posted on Physics Problems Q&A: http://physics.qandaexchange.com/?qa=616/frictionbetweentwodisks
2. Relevant equations
Second Newton's law for rotation:
$$\tau = I \alpha = RF$$
3. The attempt at a solution
I tried to solve this problem as follows:
Using Second Newton's law for rotation on disk 2R:
$$2Rf = I \alpha = \frac{1}{2} M (2R)^2 \frac{a}{2R} $$
Plugging the numbers into the equation we get:
$$f = 2N$$
OK at this point, now let's do the same on disk R:
$$Rf = I \alpha = \frac{1}{2} M (R)^2 \frac{a}{R} $$
Plugging the numbers into the equation we get:
$$f = 1N$$
So I get different values for ##f## while I have to get the same value! What am I missing on my calculations on disk A?
This problem was originally posted on Physics Problems Q&A: http://physics.qandaexchange.com/?qa=616/frictionbetweentwodisks
2. Relevant equations
Second Newton's law for rotation:
$$\tau = I \alpha = RF$$
3. The attempt at a solution
I tried to solve this problem as follows:
Using Second Newton's law for rotation on disk 2R:
$$2Rf = I \alpha = \frac{1}{2} M (2R)^2 \frac{a}{2R} $$
Plugging the numbers into the equation we get:
$$f = 2N$$
OK at this point, now let's do the same on disk R:
$$Rf = I \alpha = \frac{1}{2} M (R)^2 \frac{a}{R} $$
Plugging the numbers into the equation we get:
$$f = 1N$$
So I get different values for ##f## while I have to get the same value! What am I missing on my calculations on disk A?
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