If an atom has twelve electrons, how many electrons are in the n=1 energy level? how many electrons are in the n=2 energy level? how many electrons are in the n=3 energy level?

Suppose you use a machine that gives you a mechanical advantage of 2 to achieve an output force of 30newtons what must the input force be

Ammonia enters the expansion valve of a refrigeration system at a pressure of 10 bar and a temperature of 18oc and exits at 6.0 bar. the refrigerant undergoes a throttling process. determine the temperature, in oc, and the quality of the refrigerant at the exit of the expansion valve.

What is the coefficient of kinetic friction μk between the block and the tabletop?