Uniform Circular Motion WE WILL LEARN ABOUT UNIFORM CIRCULAR MOTION I WILL USE THE CENTRIPETAL FORCE EQUATION TO SOLVE FOR DIFFERENT VARIABLES.
Warm up 1. Turn in your Hooke s Law Lab report to the bin. 2. Take out: your elevators HW set. A blank sheet of paper. Something to write with. A calculator HW quiz will begin after I take attendance and perform the tension demo from last class.
Elevators Homework Quiz Once you finish: turn your answers into the top bin place the quiz worksheet in the bottom bin Pick up a circular motion worksheet
New Topic Uniform Circular Motion 1. Have you ever heard of centripetal motion? If so, explain. 2. Have you ever heard of centrifugal force? If so, explain.
Circular motion Uniform circular motion pertains to objects moving at a constant speed in a perfectly circular path. Circles review: How do you find the circumference of a circle? Complete questions 1-2 of the class work worksheet
New vocabulary Period, T [measured in seconds] the time required to travel once through a full cycle in UCM this means time required to travel one full circle. Frequency, f [measured in Hertz, Hz] the number of complete cycles an object completes per a given amount of time in UCM this means the number of complete circles an object completes in 1 second.
Speed in UCM vv = 2ππππ TT = 2ππrrrr Complete questions 3-4 of the worksheet
2 different types of velocity Angular velocity (ω) measured in radians/second ωω = 2ππ TT = 2πff = vv rr Linear velocity (v) measured in meters/second vv = rrωω
Period & frequency practice problems Complete questions 5-10 of the worksheet
Centripetal acceleration aa cc = vv2 rr
Circular motion demo 1 If I swing a ball around on a string and let it go. Which way will it fly?
Centripetal vs. centrifugal There is no such thing as a centrifugal force. The fake centrifugal force is a perceived force. It feels like you are being swing outward, but the opposite is true. In order for an object to travel in a circle, it requires a net force towards the center of the circle. This is the centripetal force.
Has anyone ridden a carnival ride called the Gravitron? http://www.youtube.com/watch?v=umvtizoatvu&list=pldjpetoivi XYnC7jjeq7girHp-Q-8YEQl http://www.youtube.com/watch?v=fdz9w50o-aa
Centripetal force Centripetal force always points towards the center of the circle centripetal means center seeking The centripetal force is a NET FORCE The centripetal force is often a force of tension.
Centripetal force FF cc = mmvv2 rr
Centripetal force FF cc = mmvv2 rr Do you feel more centripetal force for a sharper turn or a wider turn?
Centripetal force
Horizontal circles For simplicity, we will start by looking at cases in the horizontal plane with only one force providing the centripetal force. Example problems: #11, 12, 13
Simulating gravity in outer space If there is no force of gravity in outer space, how can a space ship fake a force of gravity so people aren t just floating around?
Faking gravity A rotating spaceship uses the normal force of the outer wall to give passengers apparent weight just like in an elevator Example problems: #14 & 15
Vertical circles If an object is being swung in a vertical circle, there are two forces acting, tension and gravity. At the top, tension and gravity act together to provide the centripetal force. At the bottom, tension has to act against gravity to provide the centripetal force.
Newton s Law of Universal Gravitation FF GG = GGmm 1mm 2 rr 2 is a centripetal force when applied to planets. G=6.67 x 10-11 N m 2 /kg 2
Orbits Gravity is supplying the centripetal force to keep planets, satellites and moons in orbit.
Satellites A geosynchronous satellite is a satellite that orbits Earth with the same period and frequency as the rotation of the earth so it stays in the same location relative to the surface of the Earth. There is only one specific altitude that a satellite can achieve this feat. Mass of the earth: 5.975 x 10 24 kg Radius of the earth: 6.371 x 10 6 m
Homework Circular HW Set quiz next class Looking ahead: Next 3 classes Lab Review Day Newton s Laws Test 2