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 Advanced Mechanics Advanced Mechanics Physics Help Forum Nov 22nd 2008, 08:24 PM #1 Junior Member   Join Date: Nov 2008 Posts: 4 Another question! Angular acceleration! Torque! HELP! I have a question that I'm not sure what to do with! HELP! A wheel of radius 0.2 m is rotating around its axis with initial angular velocity of 30 radians/s clockwise. A braking force of 6.0 N is applied tangentially at the rim. 5.0 s later the angular velocity of the wheel is 10 radians/s clockwise. (a) What is the magnitude and direction of the angular acceleration of the wheel while slowing down? (b) What is the magnitude and direction of the torque acting on the wheel? (c) What is the rotational inertia (moment of inertia) of the wheel? (d) What is the initial angular momentum of the wheel (magnitude and direction)? (e) What is the final Kinetic energy of the wheel? This is a looong question and I'm not sure what to do or use for each part.   Nov 24th 2008, 07:05 AM #2 Senior Member   Join Date: Apr 2008 Posts: 815 For a) use the relation $\displaystyle \vec \alpha= \frac{\Delta \vec \omega}{\Delta t}$. For b), you know that the torque is worth $\displaystyle \vec r \wedge \vec F$. For c) check out your notes or wikipedia. For d)$\displaystyle L_i=I_G \omega _i$. For e) $\displaystyle E_f=\frac{I_G \omega _f^2}{2}$. __________________ Isaac If the problem is too hard just let the Universe solve it.  Tags acceleration, angular, question, torque Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post oaix29201 Advanced Mechanics 1 Oct 15th 2009 12:21 AM C.E Advanced Mechanics 2 Apr 5th 2009 07:35 AM Piedog769 Advanced Mechanics 1 Apr 1st 2009 11:20 AM chino109 Advanced Mechanics 2 Mar 19th 2009 10:08 PM asi123 Advanced Mechanics 2 Nov 10th 2008 07:48 AM