Calculating Angular Momentum for a Moving Object with a Given Force

[Duderonimous]

Homework Statement

At one instant, force F=4.0j N acts on a 0.25 kg object that has a position vector r=(2.0i-2.0k) m and velocity vector v=(-5.0i+5.0k) m/s. About the origin and in unit-vector notation, what are (a) the objects angular momentum.

Homework Equations

L=I"omega", I=MR², omega=v/r

The Attempt at a Solution

Computed resulant vectors r and v and got 2rad2 m and 5rad2 m/s respectively.

Computed I, M=0.25kg and R=2rad2m. Got 2kgm².

Computed omega=v/r, v=5rad2 m/s and r= 2rad2 m. Got 2.5rad/s.

L did not come out looking so good.

Please help.

Thanks

 

[tiny-tim]

Hey there, Duderonimous!

Computed resulant vectors of r and v and got 2rad2 m and 5rad2 m/s respectively.

I don't understand what this means.

Computed I, M=0.25kg and R=2rad2m. Got 2kgm².

Computed omega=v/r, v=5rad2 m/s and r= 2rad2 m. Got 2.5rad/s.

Angular momentum (often called moment of momentum) is just r x mv, displacement "cross" momentum …

all you have to do is to "cross" the two vectors. ​

 

[Duderonimous]

Hey there, Duderonimous!


I don't understand what this means.

QUOTE]

I ment to say that I computed the magnitude of the resultant vectors. Which I got using the sqrt of the sum of the squares of the x and z components of both r and v.

Cross product eh...

Thanks.