11/21 Rotation and Torque

11/21 Rotation and Torque • Today: Start Rotational Dynamics • HW “Torque with Acceleration” Due Monday 11/25 • MCAT Review Class OrientationThursday (tonight) at 7:30 pm Haugen Lecture Hall, Med SchoolFor details attend tonight or contact: Kim Ruit: 777-2749 kim_ruit@und.nodak.edu

Displacement, x (distance moved) Average Velocity, vave (average over time) Instantaneous Velocity, v (at a particular time) Change in Velocity, v (speeding up or slowing down) Acceleration, a (how much the velocity changes each second) Force: N, W, f, T For Translation we have:

Displacement,  (angular distance moved) Average Angular Velocity, ave (time average) Instantaneous Angular Velocity,  (at a particular time) Change in Angular Velocity,  (speeding up or slowing down) Angular Acceleration,  (how much  changes each second) For Rotation we have: Torque: Nr, Wr, fr, Tr

vave = x/t  ave = /t a = v/t   = /t t = 2x/a  t = 2/ It’s all the same! About Distance About Angles The quantity “I” is the “moment of inertia” and will be given to you. Fnet = ma  net = I KET = 1/2mv2 KER = 1/2I2 WorkT = F x  WorkR =  

Example A wheel with I = 5kg m2, 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 . r = 0.5m 2m Not necessarily a disk or ring, the quantity “I” contains that information

11/21 Rotation and Torque