Conservation of Kinetic Energy During Collision

[mohabitar]

For number 3, I don't really know how to approach it. Nothing in my notes that covers such a thing. I tried using K=1/2MV^2, but that's not it. Any ideas?

 

[Doc Al]

I tried using K=1/2MV^2, but that's not it. Any ideas?

What do you mean "that's not it"? Did you calculate the initial and final kinetic energy?

 

[mohabitar]

Ohh, duh! So subtract the final kinetic from initial kinetic. Well actually it turned out that we subtract initial from final, why do we do that rather than final from initial? (how do we know whether it lost or gained energy)

 

[Doc Al]

Change always means final minus initial. If the change is positive, then you've gained energy. (Is that likely?)