Rotational Motion Summary Rotational motion is the science of how objects move in a circle. In this presentation we will talk about topics such as: Rotational Dynamics, Torque, and Equilibrium. Rotational Dynamics Angular Displacement physics.tutorvista.com As an object rotates, change in the angle is called angular displacement. The Greek letter theta is used to represent the angle of revolution Note that counter clockwise is designated as positive, while clockwise is negative. Angular Velocity Angular velocity is used to determine an object's speed of rotation. It is equal to the angular displacement divided by the time required to make the rotation. The angular velocity is represented by the Greek letter omega. Angular Acceleration Angular acceleration is the change of the angular velocity of an object. It is equal to the change in angular velocity divided by the time required to make that change. Angular acceleration is represented by the greek symbol alpha. Lever Arm and Torque Torque Torque is a measure of how effectively a force causes rotation. The magnitude of torque is the product of the force and the lever arm. Lever Arm The perpendicular distance from the axis of rotation to the point where the force is exerted. Lever arm This dude is probably exerting a lot of torque to keep that chainsaw in motion. Axis of rotation T=Fr sin 0 Torque is equal to the force times the lever arm Equilibrium Center of Mass The point on an object that moves in the same way that a point particle would move. Center of mass Stability When an object is stable as long as the direction of torque keeps it upright. An upward force must be exerted on the object to balance the downward force of gravity. If the center of mass is outside of the base of an object, it is unstable and will roll over with no additional force. If the base of the object is above the base of the object, it is stable. If the base of the object is very narrow and the center mass is high, then the object is stable, but the slightest force can tip it over. What does this have to do with Equilibrium? An object must be in static equilibrium (where both its velocity and angular velocity are at zero). For it to be in static equilibrium, it needs to be in translational equilibrium (net force equals zero) and ROTATIONAL equilibrium (where the net torque equals zero). All these things have to happen for an abject to be rotating. Such as a top or a coin. Hopefully that made sense... Citations Best Way to Trim Your Hedges. N.d. Photograph. awesomegifs.comWeb. 3 Apr 2013. <http://awesomegifs.com/2012/02/chainsaws-are-the-best-way-to-trim-your-hedges/>.

Red Wrench. N.d. Photograph. www.ux1.eiu.eduWeb. 3 Apr 2013. <http://www.ux1.eiu.edu/~cfadd/1350/09Mom/Images/redWrench.gif>.

Motorbike img846. N.d. Photograph. www.imageshack.usWeb. 3 Apr 2013. <http://img846.imageshack.us/img846/7796/mf1a0236.jpg>.

Desk Flip face meme. N.d. Photograph. www.alltheragefaces.comWeb. 3 Apr 2013. <http://alltheragefaces.com/face/angry-desk-flip>.

Zitzewitz, , Ellott, Haase, Harper, Herzog, Nelson, Schuler, and Zorn. Physics:Principles and problems. McGraw Hill, Print.

"Physics:Rotational Motion." www.cliffnotes.com. N.p.. Web. 4 Apr 2013. <http://www.cliffsnotes.com/study_guide/Rotational-Motion-of-a-Rigid-Body.topicArticleId-10453,articleId-10419.html>.

By Blaine Wolfe and Devin Ross

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