A missle coliding witha satelite

[talolard]

Homework Statement

I typed it in word. Is this correct?
Thanks
Tal

 

[kuruman]

Isn't the satellite moving in a circular orbit and the missile in the radial direction? It seems to me that their velocities are perpendicular to each other which means you have a collision in two dimensions.

 

[talolard]

I agree but i don't see what that means.

 

[kuruman]

I agree but i don't see what that means.

It means that the sum of the two momentum vectors before the collision is equal to the single momentum vector after the collision. How do you two add vectors that are perpendicular to each other?

 

[talolard]

Standard vector addition?
I don't see how vectors are relevant though because all of my quantities are scalrs and not vectors.

I solved this problem correctly previously using conservation of energy but I don't understand why momentum is wrong.

 

[kuruman]

Standard vector addition?
I don't see how vectors are relevant though because all of my quantities are scalrs and not vectors.

The initial momentum of the satellite is not in the same direction as the initial momentum of the missile. Therefore, to find the total initial momentum, you need to add the two as vectors. You need the total initial momentum to use in the momentum conservation equation.

I solved this problem correctly previously using conservation of energy but I don't understand why momentum is wrong.

It is correct to use energy conservation after the collision is completed, however the solution will not be correct unless the velocity of of the composite mass immediately after the collision is calculated correctly.