Removing heat from a system changes the internal energy of the system. Which scenario correctly represents this case?
A.) placing a bowl of ice cubes in a closed room
B.) adding ice cubes into a thermos of hot coffee
C.) switching on the air conditioning of a closed room
D.) placing a thermos with hot coffee in an air conditioned room

Abird flies directly overhead from where you stand at an altitude of 300.0 m and at a speed horizontal to the ground of 20.0 m/s. the bird has a mass of 2.0 kg. the radius vector to the bird makes an angle \thetaθ with respect to the ground. the radius vector to the bird and its momentum vector lie in the xyxy-plane. what is the bird’s angular momentum about the point where you are standing?