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Old Oct 14th 2009, 10:16 PM   #1
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net torque and acceleration

70 cm diameter cylindrical disk has a mass of 10 kg and accelerates uniformly from 150 rpm to 300 rpm in 4 sec. a) find angular accleration. b) what are th radial and tangential components of linear accleration for a point on the edge of the wheel. C) what is th net torque acting on the wheel.

I found the part a and part c. In part a, which is a=w/t= 15.7rad/s /4 sec=3.93 rad/s^2

for C, I have T=1/2 MR^2 * 3.93 = 2.4NM

but I stock on next b problems. can any one help me out?

finding radial and tangential acceleration, radial is centrepedal, right? which is a_c=v^2/r, and a_tan=v/t.. I plug in the numbers, but I don't get the right answer.
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Old Oct 15th 2009, 12:21 AM   #2
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Calculate the velocity of a point on the edge of the disk for both 150 rpm and 300 rpm using v = r x omega where omega is the angular velocity.

The difference in velocities divided by 4 sec will give you the tangential accln.

The centripetal or radial accln is given by v^2 / r.

The net acceleration is the vector sum of both.
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