A bullet hits balk of 5kg on a rope of 2m lenths. Bullets mass 2gr, velocity unknown. Plastic collission, balk goes upat 45 degrees.
When i solve it with energy equations i get
V(of balk and bullet) = sqrt(2gh)=3.38 m/s. (potential energy of total mass)
Now i need to find a velocity of bullet at t(0).
Here is the trick
when i solve it using momentum i get:
But!! when i solve it using energy i got
Thinking about that we used the potential energy to calculate a balk speed and taking into account an absolute plastic collision i dont know why is the differense?
Thanks for any help.