- #1

YanZhen

- 10

- 0

- Homework Statement
- The mass of the particle is m,the equation of motion is r=acosωti+bsinωtj.a and b are constant.Calculate the angular momentum of a particle at any time.

- Relevant Equations
- L=P*r=m*v*r

v=dr/dt

i,j,k arevector

I know L=P*r=m*v*r=m(acosωti+bsinωtj)*(-aωsinωti+bωcosωtj)=mabw((cos^2)ωt+(sin^2)ωt)k=mabωk.

but why m(acosωti+bsinωtj)*(-aωsinωti+bωcosωtj)=mabw((cos^2)ωt+(sin^2)ωt)k.I need some detail.

please help me.

I know L=P*r=m*v*r=m(acosωti+bsinωtj)*(-aωsinωti+bωcosωtj)=mabw((cos^2)ωt+(sin^2)ωt)k=mabωk.

but why m(acosωti+bsinωtj)*(-aωsinωti+bωcosωtj)=mabw((cos^2)ωt+(sin^2)ωt)k.I need some detail.

please help me.