1. A 3.0-g bullet traveling at a speed of 400 m/s enters a tree and exits the other side with a speed of 200 m/s. Where did the bullet's lost KE go, and what was the energy transferred? 2. ΔKE+ΔPE+ΔU = Q-W 3. The only questions I have about this problem are why does the Work=0, Heat=0, and why does the ΔPE=0?