11/22 Rotation and Torque  Today: Rotational Dynamics  HW “Pulling the Wheel” Due Wednesday 11/27  Class canceled 12/2, Not this coming Monday!

It’s all the same! v ave =  x/  t   ave =  /  t a =  v/  t   =  /  t  t =  2  x/a   t =  2  /  About DistanceAbout Angles F net = ma   net = I  The quantity “I” is the “moment of inertia” and will be given to you. KE T = 1 / 2 mv 2  KE R = 1 / 2 I  2 Work T = F  x  Work R =  

Measuring Angles, Radians One Rad of rotation = one radius of translation (rolling without slipping and strings wrapped around pulleys)  x = r  v =  r  v =  r v ave =  ave r a =  r 1 Rad 1 radius (r) r r

Example A wheel with I = 5kg m 2, is mounted on a frictionless axle. A rope wrapped around its outer rim is pulled with a force T = 50N for a distance of 2m. Find everything, starting with . 2m r = 0.5m Not necessarily a disk or ring, the quantity “I” contains that information