Apellet gun is shot at a cardboard box of mass m2 = 0.65 kg on a frictionless surface. the pellet has a mass of m1 = 0.0145 kg and flys at a velocity of v1 = 79 m/s. it is observed that the box is moving at a velocity of v2 = 0.43 m/s after the pellet goes through it.1. write an expression for the magnitude of the bb's velocity as it exits the box vf.
2. what is the bb's final velocity vf, in meters per second?
3. if the bb doesn't exit the box, what will the velocity of the box v'2, be in meters per second?

Asteel tube (k=50 w/mk) of inner and outer diameter di = 20mm and do=26mm, respectively, is used to transfer heat from hot gases flowing over the tube (h-hot = 200w/m2k) to cold water flowing through the tube (h-cold = 8000 w/m2k). what is the cold-side overall heat transfer coefficient uc? to enhance heat transfer 16 straight fins of rectangular profile are installed longitudinally along the outer surface of the tube. the fins are equally spaced around the circumference of the tube, each having a thickness of 2mm and a length of 15mm. what is the corresponding overall heat transfer coefficient uc? *solve for uc in both cases*