Basic Momentum and Energy!!!! 1. (part 1 of 2) A 4.78 g bullet moving at 510.8 m/s penetrates a tree trunk to a depth of 4.93 cm. a) Use work and energy considerations to find the magnitude of the force that stops the bullet. Answer in units of N. for this i did 1/2mv^2=w=fd so 1/2(.00536)(681.8)^2=w=fd 1245.801323=fd 1245.801323=f(.0379) and i solved for f and got 32870.74731 2. (part 2 of 2) b) Assuming that the frictional force is constant, determine how much time elapses between the moment the bullet enters the tree and the moment the bullets stops moving. Answer in units of s. for this one i just did vf^2=vi^2+2at. is that correct?? THANK YOU!!