A cannon fires a shell straight upward; 1.9 s after it is launched, the shell is moving upward with a speed of 17 m/s. Assuming air resistance is negligible, find the speed (magnitude of velocity) in meters per second of the shell at launch and 5.5 s after the launch.

conservation of mass

mass before something happens = mass afterwards

blue light is scattered in different directions by the tiny molecules of air. blue is scattered more than other colours because it has a shorter distance to travel which results in smaller waves. this is why we see a blue sky most of the time.