ch9_esjp

**Chapter 9-Circular Motion**

__Sections: __  **//Ch.9 Section 1-Rotation and Revolution   //**
 * 1) Rotation and Revolution
 * 2) Rotational Speed
 * 3) Centripetal Force
 * 4) Centripetal and Centrifugal Force
 * 5) Centrifugal Force in a Rotating Reference
 * 6) Simulated Gravity


 * __axis__- the straight line around which an object may rotate or revolve.
 * <span style="font-family: Georgia,serif;">__rotation (spin)__- a spinning motion that takes place when an object rotates about an axis; located within the object.
 * <span style="font-family: Georgia,serif;">__revolution__- motion of an object turning around an axis; located outside the object.

<span style="font-family: Georgia,serif;">//The difference of rotation and revolution and shown here.// <span style="font-family: Georgia,serif;"> <span style="font-family: Georgia,serif;">**//Ch.9 Section 2-Rotational Speed//**

<span style="font-family: Georgia,serif;"> //As you can see, as the person moves toward the outer edge of a rotating platform, her linear speed, represented by the blue arrows, must increase if she is to maintain her position relative to the ground.// <span style="font-family: Georgia,serif;">//The tangential speed, shown with the red arrows, is the path of the objects motion if it were to separate from it's rotation around the circle.// <span style="font-family: Georgia,serif;">//As shown in this diagram, the two speeds, tangential and rotational, are represented in one equation:// or <span style="font-family: Georgia,serif;">//**Ch.9 Section 3-Centripetal Force**//
 * <span style="font-family: Georgia,serif;">__linear speed__- the path **distance moved** per unit of time; also called speed.
 * <span style="font-family: Georgia,serif;">With linear speed, a point on the outer edge of an object moves a greater distance in one rotation than a point closer to the center of the object.
 * <span style="font-family: Georgia,serif;">This means that the point on the outer edge has a greater linear speed than the point closer to the axis.
 * <span style="font-family: Georgia,serif;">__tagential speed__- the speed of an object moving along a **circular path**.
 * <span style="font-family: Georgia,serif;">This term is used because the direction of the object's motion is always tangent to the circle.
 * <span style="font-family: Georgia,serif;">When dealing with circular motion, both linear speed and tangential speed can be used to describe the object in motion.
 * <span style="font-family: Georgia,serif;">Tangential speed depends on the rotational speed and distance from the axis.
 * <span style="font-family: Georgia,serif;">At the axis of an object, there is no tangential speed
 * <span style="font-family: Georgia,serif;">__rotational speed (angular speed)__- the **number of rotations** or **revolutions** per unit of time; often measured in rotations or revolutions per second or per minute (RPM).
 * <span style="font-family: Georgia,serif;">All parts of a rotating object rotate around the axis in the same amount of time.
 * <span style="font-family: Georgia,serif;">This means, that anywhere on the object, the rate of rotation is the same.
 * <span style="font-family: Georgia,serif;">Tangential speed is directly proportional to the rotational speed and the radius distance from the axis of the object.
 * <span style="font-family: Georgia,serif;">Tangential speed ~ radial distance x rotational speed
 * <span style="font-family: Georgia,serif;">At the center of an object, there is rotational speed. As you move further from the axis, the tangential speed increases while the **rotational speed remains the same**.
 * tangential speed= radial distance * angular speed**
 * v = (r)(w)** <span style="font-family: Georgia,serif;">

<span style="font-family: Georgia,serif;">//As you can see by this picture, when on a roller coaster that has a loop, the passengers experience centripetal force, as well as inertia. Centripetal force can be found with the following equation:// //where Fc= Centripetal Force ;m= mass; r= radius; v= tangential speed; w= angular speed// <span style="font-family: Georgia,serif;"> <span style="font-family: Georgia,serif;">**//Ch.9 Section 4-Centripetal and Centrifugal Forces//**
 * <span style="font-family: Georgia,serif;">__centripetal force__- a center directed force that causes an object to move in a curved (sometimes circular) path.
 * <span style="font-family: Georgia,serif;">Centripetal means "center-seeking" or "toward the center".
 * <span style="font-family: Georgia,serif;">It is any force that is at a right angle to the path of a moving object that has a circular motion.
 * Fc = ((mv)^2) / (r) = ((m)(r)(w))^2**

//<span style="font-family: Georgia,serif;">As seen in this picture, the people on the ride experience an outward force as the swings move in a circular pattern. // <span style="font-family: Georgia,serif;"> <span style="font-family: Georgia,serif;">**//Ch.9 Section 5-Centrifugal Force in a Rotating Reference//**
 * <span style="font-family: Georgia,serif;">__centrifugal force__- an apparent outward force on a rotating or revolving body. It is fictitious in the sense that it is not part of an interaction, but is due to the tendency of a moving body to move in a straight line path.
 * <span style="font-family: Georgia,serif;">Centrifugal force means "center-fleeing" or "away from the center".
 * <span style="font-family: Georgia,serif;">One may believe that centrifugal force pulls something outward, while reality is that there is only an **absence of centripetal force**.
 * <span style="font-family: Georgia,serif;">The "centripetal-force effect" is only attributed to inertia (which is the tendency of a moving body to follow a continuous straight line path)


 * <span style="font-family: Georgia,serif;">In a rotating reference, a centrifugal force feels as though it acts like gravity.
 * <span style="font-family: Georgia,serif;">However, both centripetal force (towards the center of the axis), and the centrifugal force (pulling outward) are acting upon the object in the rotating reference.
 * <span style="font-family: Georgia,serif;">Gravity can **only** occur between two masses (our mass and the earth for example).
 * <span style="font-family: Georgia,serif;">In a rotating object with a centrifugal force, there is no second mass for the object to be attracted to. This means that a centrifugal force is only an **effect of rotation** (not a true force).
 * <span style="font-family: Georgia,serif;">It is because of this "false force" that physicists refer to centrifugal force as a **fictitious force**.
 * <span style="font-family: Georgia,serif;">It is important to remember that centrifugal force is **always** present in a rotating reference.

<span style="font-family: Georgia,serif;">//This image shows the centrifugal force moving outward during a rotation.// //**<span style="font-family: Georgia,serif;">Ch.9 Section 6-Simulated Gravity **//

<span style="font-family: Georgia,serif;"><span style="font-family: Georgia,serif;"> <span style="font-family: Georgia,serif;">//Simulated gravity can be represented by a space station.// <span style="font-family: Georgia,serif;"> <span style="font-family: Georgia,serif;">//**Practice Problems**//
 * <span style="font-family: Georgia,serif;"><span style="font-family: Georgia,serif;">Gravity is **simulated** by centrifugal force
 * <span style="font-family: Georgia,serif;"><span style="font-family: Georgia,serif;">For example:
 * <span style="font-family: Georgia,serif;"><span style="font-family: Georgia,serif;">If someone were inside a wheel the direction **"up"** is **toward** the center of the wheel and **"down"** is radically **outward**.
 * <span style="font-family: Georgia,serif;"><span style="font-family: Georgia,serif;">**Doubling** the distance from the axis of rotation **doubles** the centripetal/centrifugal acceleration; **tripling** the distance, **triples** the acceleration, and so on.
 * <span style="font-family: Georgia,serif;"><span style="font-family: Georgia,serif;">At the axis, the radical distance is **zero** and there is **no** acceleration due to rotation.
 * <span style="font-family: Georgia,serif;"><span style="font-family: Georgia,serif;">Small-diameter structures would have to rotate at high speeds to provide a **simulated** gravitational acceleration of **<span style="font-family: Arial,Helvetica,sans-serif;">1g .**

<span style="font-family: Georgia,serif;">The following practice problems were assigned by Mr. Strong and are found in the textbook:

Pages 133-134 Review Questions # 3, 4, 7, 8, 10, 12, 13, 15, 16, 17 Pages 134-135 Think and Explain # 1, 2, 3, 4, 7, 8, 9, 10, 11 Page 135 Think and Solve # 1, 2, 3, 4


 * //<span style="font-family: Georgia,serif;">Sources //**

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 * <span style="font-family: Georgia,serif;">Conceptual Physics: Third Edition with Expanded Technology by Paul G. Hewitt
 * <span style="font-family: Georgia,serif;"><span style="font-family: Georgia,serif;">http://www.intertronics.co.uk/images/arerotation.jpg
 * <span style="font-family: Georgia,serif;"><span style="font-family: Georgia,serif;">[|http://www.ux1.eiu.edu/~cfadd/1150/03Vct2D/Images/tang1.gif]
 * <span style="font-family: Georgia,serif;"><span style="font-family: Georgia,serif;">http://archives.sensorsmag.com/articles/0903/53/fig2.gif
 * <span style="font-family: Georgia,serif;">http://www.esotericscience.com/rotorclock.jpg
 * <span style="font-family: Georgia,serif;">http://apollo.lsc.vsc.edu/classes/met130/notes/chapter8/graphics/centrifugal.free.gif
 * <span style="font-family: Georgia,serif;">http://www.mansfieldct.org/schools/mms/staff/hand/lawsCentripetalForce_files/image008.jpg
 * <span style="font-family: Georgia,serif;">http://farm1.static.flickr.com/26/37643561_1c20cd1ab0.jpg?v=0
 * <span style="font-family: Georgia,serif;">http://www.racetomars.ca/mars/ed-module/artificial_gravity/images/rotation1.jpg

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