You know that a collision must be "elastic" if:

Question

The momentum of the two-object system doesn't change
The sum of the final kinetic energies equals the sum of the initial kinetic energies
There is no change in the internal energies of the objects (thermal energy, vibrational energy, etc.)
The colliding objects stick together The colliding objects are stretchy or squishy
which are true?

Answer 1

b.
c.

a and d are nor revealing to determine elasticity.

Answer 2

thanks,
can you help me with this one

What is the angular momentum A if A = <7, 5, 0> m and = <-20, 10, 0> kg·m/s?

Answer 3

I thought you just do 7(20)+(5)10

Answer 4

If it is in three orthagonal dimensions, you have to

sqrt((140^2)+50^2 + 0^2)