Week 10 Rotation of Rigid Bodies 2

Question 1

what is the non slip CoM velocity equation

Answer 1

vcm = ωR

Question 2

what is the total KE of a rotational body system

Answer 2

KEtot = 1/2Icmω^2 + 1/2Mvcm^2

Question 3

why isn’t friction involved in rolling motion

Answer 3

when a wheel is rolling on a horizontal plane at constant speed the instantaneous point of contact is momentarily at rest so there is nothing for friction to resists

Question 4

what must be the first step for analysing a body undergoing translational and rotational motion

Answer 4

think in terms of CoM

Question 5

what is true of all rotating motion

Answer 5

even if it doesn’t start with non slip conditions will eventually end up obeying non slip conditions

Question 6

what is the angular momentum vector equation

Answer 6

L = rp

Question 7

what is the angular momentum magnitude equation

Answer 7

L = mrvsinθ

Question 8

how does angular momentum relate to torque

Answer 8

dL/dt = T

the rate of change of angular momentum of a particle equals the net torque acting on that particle

Question 9

what can be said about angular momentum when there is an absence of an external force

Answer 9

angular momentum is conserved

Question 10

what is the total angular momentum of a system

Answer 10

sum of angular momentum of the individual constituents

Question 11

what is the angular momentum equation for a rigid body rotating about an axis of symmetry

Answer 11

L and ω act in the same direction so

L = Iω