A bullet of mass 4.2 g strikes a ballistic pendulum of mass 2.0 kg. The center of mass of the pendulum rises a vertical distance of 18 cm. Assuming that the bullet remains embedded in the pendulum, calculate the bullet’s initial speed.
2. Relevant equations
3. The attempt at a solution
I started by converting everything into the correct units:
Bullet’s mass(m)= 0.0042 kg Ballistic pendulum(M)= 2 kg Vertical distance(h)= 0.18 m
Then used this equation to solve for the velocity of the bullet after the collison:
Then this equation to get the bullet’s initial speed:
I’m not sure what I’m doing wrong, my online homework only wants 2 significant digits.
Also, if someone could explain to me where these equations came from I would really appreciate it. I’m having some trouble understanding how to manipulate the energy equations to wind up with the ones I used in the problem.