A 90.00-kg hockey goalie, at rest in front of the goal, stops a puck (m = 0.16 kg) that is traveling at 30.00 m/s. at what speed do the goalie and puck travel after the save?

5.3 cm/s This is a matter of conservation of momentum. Since there's no mention of the puck rebounding, I will consider this to be a totally non-elastic collision. So, let's determine the starting momentum of the system. Goalie is at rest, so his momentum is 0. Puck is moving at 30.00 m/s with a mass of 0.16 kg, so: 30.00 m/s * 0.16 kg = 4.8 kg*m/s So the starting momentum is 4.8 kg*m/s moving towards the goal. After the collision, the puck and goalie will have the same momentum. So figure out the mass of the new system: 90.00 kg + 0.16 kg = 90.16 kg And divide the system momentum by the system mass: 4.8 kg*m/s / 90.16 kg = 0.053238687 m/s Finally, round to the least precise datum, so the result to 2 significant figures is 0.053 m/s, or 5.3 cm/s.