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Chapter 8 Rotational Kinematics Rotation – (rotate) To spin on an internal axis. Revolution – (revolve) To move around an external axis. The Record Player or Turntable A penny rotates on the turntable at 45 RPM How fast is the penny moving? Angular Velocity Tangential Velocity (Rotational Speed) (Linear Speed) 45 revolutions/minute or 45 x (2) = 282.7 rad/min Depends on the distance (r) away from the center Tangential Velocity = Linear Velocity = v Angular Velocity = Rotational Velocity = ω V depends on distance from axis rotation. v r What is pi? Pi is the ratio of a circle’s circumference to diameter. Circumference (C) Diameter (d) 3.14159... Arc length s = arc length r = radius What is a radian? A radian is a unit used for measuring angles. s = arc length r = radius Angles can be measured in degrees or radians 180 Angular Displacement (Δθ) - Can be measured in 1) degrees 2) radians 3) revolutions (1 rev = 360°) Angular Velocity (ω) - t Measured in rad/sec or rev/min (etc) Angular Acceleration (α) - t Measured in rad/sec2 or rev/min2 (etc) v f vo at f o t x vot at 1 2 x vt t v v 2ax 2 2 f 2 o o t t 2 1 2 2 2 f 2 o ASSIGN: Ch. 8 #2,12,16,32 p. 231 due Friday