Chapter 5 Notes

Ty Wixom 11/29/09 Physics Chapter 5 Notes 5-1 • • • • •

Uniform circular motion – object moving in a circular motion at a constant velocity o Magnitude is constant, velocity is always changing Centripetal Accel. – “center-seeking” acceleration Radial Accel. – acceleration along radius, toward center (Ar) o Ar = v^2/r Object moving in a circle of radius r with constant speed v has an acceleration whose direction is toward the center of the circle and whose magnitude is Ar = v^2/r T = 1/f

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Net force is directed towards the center of the circle and must be applied by other objects Net F = mAr =mv^2/r

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If Net F is not directed towards center there are 2 components: 1 directed towads the center and 1 tangent to the circle Tangent component is equal to the rate of change of the magnitude of velocity of the object: Atan = delta v/delta t

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Law of Universal Gravitation: every particle in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them. This force acts along the line joining the two particle. o F= Gm1m2/r^2

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Satellites stay up because of their tangential speed

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Kepler’s laws of planetary motion: o 1st – The path of each planet about the sun is an ellipse with the sun at one focus o 2nd – Each planet moves so that an imaginary line drawn from the sun to the planet sweeps out equal areas in equal periods of time

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o 3rd – The ratio of the squares of the periods of any 2 planets revolving about the sun is equal to the ratio of the cubes of their mean distances from the sun.