Radians and Degrees • In degrees, once around a circle is 360° • In radians, once around a circle is 2π • A radian measures a distance around an arc equal to the length of the arc’s radius • Δs=C=2πr Linear vs. Angular Displacement • Linear position / displacement given by Δr or Δs • Angular position / displacement given by Δθ • s=rθ • Δs=rΔθ Linear vs. Angular Velocity • Linear speed / velocity given by v ⃗ • Angular speed / velocity given by ω ⃗ • v ⃗=(ds ⃗)/dt • ω ⃗=(dθ ⃗)/dt Direction of Angular Velocity Converting Linear to Angular Velocity Linear vs. Angular Acceleration • Linear acceleration is given by a ⃗ • Angular acceleration is given by α ⃗ • a ⃗=(dv ⃗)/dt • α ⃗=(dω ⃗)/dt Kinematic Variable Parallels Variable Translational Angular Displacement Δs Δθ Velocity v ⍵ Acceleration a ⍺ Time t t Variable Translations Variable Translational Angular Displacement s=rθ θ=s/r Velocity v=rω ω=v/r Acceleration a=rα α=a/r Time t=t t=t Kinematic Equation Parallels Centripetal Acceleration Example: Wheel in Motion • A wheel of radius r and mass M undergoes a constant angular acceleration of magnitude ⍺. • What is the speed of the wheel after it has completed on complete turn, assuming it started from rest? 2003 Free Response Question 3 2014 Free Response Question 2
