Quick Review of Last Friday Last Friday The kinematics of uniform circular motion TODAY – The dynamics of uniform circular motion – Circular orbits of satellites – Newton’s law of gravity
Uniform Circular Motion Uniform magnitude of velocity (speed) is constant
Going from angular velocity to angular displacement:
Uniform Circular Motion Uniform magnitude of velocity (speed) ω, is constant But α is not zero because direction of velocity is changing.
Centrifugal Force NOT A REAL FORCE What supplies the force to make your acceleration such as to cause you to move in a circle? Centripetal FORCE—towards the center. This is the real force involved. v a
Vertical Circle Ferris wheel—free body diagram when at top F NET w=mg n TOP
Ferris Wheel At the bottom “Apparent weight” = n is greater at bottom of cycle than at top n BOTTOM w=mg
Centrifuges Diameter = 18 cm Centripetal acceleration = 250,000 g What is the frequency? Rev/sec and rpm Apparent weight of a 3 mg mass in this machine?
Workbook due today Go to board and explain – 1a and c – 1b and d – 2 – 3 – 4 – 5 – 6a,b and c
A cyclist goes around a circular track at constant speed. Since her speed is constant, her acceleration is zero 1.True 2.False 3.Need more information
6.15 A 1500 kg car drives around a flat 200m diameter circular track. What are the magnitude and direction of the net force on the car? What causes this force?
When a ball on the end of a string is swung in a vertical circle: What is the direction of the acceleration of the ball? 1.Tangent to the circle, in the direction of the ball’s motion 2.Toward the center of the circle