lecturenotes-Feb1

lecturenotes-Feb1 - This is what will be given. Math...

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This is what will be given. . Math Vectors Kinematics Projectile motion Newton’s 2nd law Friction/circular motion
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C Uniform Circular Motion, Centripetal Force In Chapter 4 we saw that an object that moves on a circular path of radius r with constant speed v has an acceleration a. The direction of the acceleration vector always points toward the center of rotation C (thus the name centripetal ). Its magnitude is constant and is given by the equation 2 . v a r = If we apply Newton’s law to analyze uniform circular motion we conclude that the net force in the direction that points toward C must have magnitude: This force is known as “ centripetal force. 2 . mv F r =
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Question: What provides “force” for centripetal acceleration? - friction (points parallel to surface - opposes motion) - gravity (points downward with magnitude g) - normal (points perpendicular to surface) A centripetal force accelerates a body by changing the direction of the body’s velocity without changing the body’s speed F cent = ma cent = mv 2 r because v and r are constant, magnitude of F cent (& a cent ) is constant. direction of F cent (& a cent ) towards center (constantly changing direction!!) - tension (points along the direction of string/rope) The notion of centripetal force may be confusing at times. A common mistake is to “invent” this force out of thin air. Centripetal force is not a new kind of force. It is simply the net force that points from the rotating body to the rotation center C.
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Recipe for Problems That Involve Uniform Circular Motion of an Object of Mass m on a Circular Orbit of Radius r with Speed v m v x y . C r Draw the force diagram for the object. Choose one of the coordinate axes (the y-axis in this diagram) to point toward the orbit center C. Determine Set 2 , . net y mv F r = , . net y F
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C y A hockey puck moves around a circle at constant speed v on a horizontal ice surface. The puck is tied to a string looped around a peg at point C. In this case the net force along the y-axis is the tension T of the string. Tension T is the centripetal force.
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This note was uploaded on 05/20/2011 for the course PHYS 2101 taught by Professor Grouptest during the Spring '07 term at LSU.

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lecturenotes-Feb1 - This is what will be given. Math...

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