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
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.
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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