physic help needed
A 5.00g bullet is fired into a 900g block of wood suspended as a ballistic pendulum. The combined mass swings up to a height of 8cm. What was the kinetic energy of the bulley immediately before the collision?
The answer is 129J,but i dont get how to solve it. I think you got to use the potiental energy formula and kinetic energy formula,but im not sure.
January 4, 2013
1 Comment • Newest first
There's some momentum involved.
1) Kinetic Energy of combined mass=Gravitational Potential Energy
2)Find the velocity of the combined mass.
3) Conservation of momentum, initial momentum of the bullet + initial momentum of the block= momentum of the combined mass. Block wasn't moving so it's 0. Initial momentum of the bullet=momentum of the combined mass. Solve for initial velocity of bullet.
4) Use the velocity you found to find the Kinetic energy of the bullet.
EDIT: Just in case, mass*velocity=momentum