Prove that in the absence of external forces, the total angular momentum (defined asl = α r α × p α ) of an n-particle system is conserved. [hints: you need to mimic the argumentfrom (1.25) to (1.29). in this case you need more than newton’s third law: in addition you needto assume that the interparticle forces are central ; that is f αβ acts along the line joining particlesα and β.]

A248-g piece of copper is dropped into 390 ml of water at 22.6 °c. the final temperature of the water was measured as 39.9 °c. calculate the initial temperature of the piece of copper. assume that all heat transfer occurs between the copper and the water. remember, the density of water is 1.0 g/m

Aphysical change is a change in the size, shape,, or stafe of matter true or false

This is important 1. what happens to the speed of molecules in water vapor when it condenses to form a liquid? (2 points) the molecules slow down. the molecules speed up. the molecules slow down and then speed up. the molecules speed up and then slow down. 2. how might human activities change to compensate for a decrease in water supplies? (2 points) humans might build a factory. humans might build drainage systems. humans might extract more water from the ground. human behavior does not change because of the water cycle. i'll be grateful if anyone can answer these 2 questions !