On an ice skating rink, a girl of mass 50 kg stands stationary, face to face with a boy of mass 80 kg. the children push off of one another, and the boy moves away with a velocity of +3 m/s. what is the final velocity of the girl?

"an open tank has the shape of a right circular cone. the tank is 6 feet across the top and 5 feet high. how much work is done in emptying the tank by pumping the water over the top edge? note: the density of water is 62.4 lbs per cubic foot."

Which two particles are found in the center of an atom

I’ve been stuck on this for a while