(adsbygoogle = window.adsbygoogle || []).push({}); 1. The stone of mass m=100 kg is placed inside the cup at the end of a rotating arm of length l=3 m. If arm is released from rest at theta=0 and its angular acceleration is given as theta (double dot) = 5 rad/s2 cos t (a) find the acceleration of the stone with theta=pi/4 rad; (b) what is the force acting on the stone from the cup at this instant (include gravity); (c) at what time does the stone fly off the arm?

2. I'm thinking the equation to start with is a(p)=(r(double dot)-r*theta(dot)2)e(r) + (r*theta(double dot)+2r(dot)theta(dot))e(theta)

3. Using the above equation, with the assumption that r(dot) and r(double-dot) are zero, I found that the acceleration at pi/4 was -14.8e(r) + 2.34 e(theta). But the answer given is -21.71e(r) + 12.64e(theta). I cannot figure out what I did wrong. Can anyone help me?

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# Dynamics radial acceleration problem: Stone is placed in cup at end of rotating arm

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