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Circular Motion and Gravitation

Circular Motion and Gravitation. Circular Motion. As an object moves in a circle, it is constantly changing its direction. If the object’s direction is constantly changing what does this mean about its velocity….even if it has a constant speed?

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Circular Motion and Gravitation

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  1. Circular Motion and Gravitation

  2. Circular Motion • As an object moves in a circle, it is constantly changing its direction. • If the object’s direction is constantly changing what does this mean about its velocity….even if it has a constant speed? • Can we use the “normal” acceleration equation for this? • http://www.physicsclassroom.com/mmedia/circmot/cf.cfm

  3. Where do we see circular motion in everyday life? • Merry-Go-Round • Centrifuge Ride at a Fair • NASCAR car on a track • Driving on a banked curve • Swinging your key chain in the air • Space stations • Atoms around the nucleus • Plants orbiting the Sun

  4. What does circular motion look like? • Flicker centripetal force • http://www.flickr.com/photos/physicsclassroom/galleries/72157625140509911/ • Show Coaster simulation • http://www.compadre.org/Repository/document/ServeFile.cfm?ID=8228&DocID=873 • Particle in a jar • http://www.compadre.org/Repository/document/ServeFile.cfm?ID=11235&DocID=2277 • Physics Vectors and Circular Motion • http://regentsprep.org/Regents/physics/phys06/bcentrif/

  5. Centripetal Force • The net force acting upon such an object is directed towards the center of the circle. • Without such an inward force, an object would continue in a straight line, never deviating from its direction. • Centripetal force is equal to mass times acceleration of centripetal force (ac=v2/r) Ft=mac

  6. Centripetal Acceleration • An object undergoing uniform circular motion is moving with a constant speed. • It is accelerating due to its change in direction. • The direction of the acceleration is inwards. • Time (t) = time it takes for one revolution to occur • V = velocity • r = radius (half diameter), typically, equal to length of string ac=v2/r ac=(4Π2r)/T2 • What would happen if the string snapped? • An object undergoing uniform circular motion will continue in the same direction.

  7. Where do we see this? • Roller Coasters! • The centripetal force is the reason we only have to have lap bars in some roller coasters, even though you flip upside down!

  8. Gravitation • Newton was able to draw an important conclusion about the dependence of gravity upon distance • the force of gravitational attraction between the Earth and other objects is inversely proportional to the distance separating the earth's center from the object's center. • Basically….twice the distance=1/4 as strong a pull from gravity • Steve Spangler • http://www.youtube.com/watch?v=yyDRI6iQ9Fw

  9. Inverse Square Law F=1/r2(r in this equation is equal to distance)

  10. Newton’s Law of Universal Gravitation • Gravitational Force is a field force that is based on an amount of mass two objects have which make them attract to each other. FGravitation= G (m1m2/r2) • G = 6.67E-11 Nm2/kg2 • m1or m2= mass of objects one and two • r = distance between two centers of the two masses

  11. PhET Lab Simulation • Change the variables to see the effect on Gravitational Force • http://phet.colorado.edu/en/simulation/gravity-force-lab

  12. Extra Help • http://regentsprep.org/Regents/physics/phys06/bcentrif/ • http://www.physicsclassroom.com/Class/circles/U6L1a.cfm • http://www.youtube.com/watch?v=_mCC-68LyZM • http://www.youtube.com/watch?v=Vpyx7Gu0hos • http://www.youtube.com/watch?v=H9fe_4QB7Uk • http://www.youtube.com/watch?v=Q9ZVCnD9t18

  13. Answers to Problems • r = 128.57 m • A) v = 3.65 m/s B) ac = .51 m/s2 • F = 8.24 N • No, because it is change direction; ac= 6.581 m/s2; 0 m/s because of changing direction • 1) 8.004 x 10^-10 N • 2) 8.00 x 10^-9 N • 3) 7.31 x 10^28 kg

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