Uniform Circular Motion Chapter 10

Circle Circumference C = π D = 2 π r Area A = π r2

Rotation vs. Revolution When an object turns about an internal axis The Earth rotates creating day and night Revolution When an object turns about an external axis The Earth revolves around the Sun

Speed Linear Speed Tangential Speed Rotational Speed Distance traveled per unit time Tangential Speed Speed of something moving in a circular path Speed is directed tangent to the circle Rotational Speed Number of rotations per unit time (Angular Speed)

Centripetal Force, Fc Fc Force that keeps an object moving in a circular path Directed towards center of circle Without it, object would continue in a straight line (N1L) Fc

Centripetal Acceleration Change in velocity (magnitude or direction) that keeps object moving in a circle Directed towards center of circle

Centripetal Force, Fc

Centripetal Force, Fc Centripetal Force is provided by another force Tension provides Centripetal Force T Fg

Centripetal Force, Fc At top, weight provides Centripetal Force At bottom, Normal Force provides Centripetal Force FN Fg

Centrifugal Force Not Real, Does not exist Result of Inertia (N1L) Imagine a box sitting on the front seat of an old car with vinyl bench seat

Centrifugal Force While car is moving forward, box’s inertia is moving forward As car turns left, box continues forward, appears to move right

Centripetal Force Example A 50kg skater going around a 10m curve at 10m/s. What is the centripetal force?

Another Example How fast is a 1200kg car moving around a 100m curve to have a centripetal force of 7500N?