Which of the following groups have seven valence electrons and are very reactive? Column 1 alkali metals
Column 2 alkaline earth metals
Column 17 halogens
Column 18 noble gases

The of a machine determines its "usefulness." a. input force b. output force c. mechanical advantage

Aball tossed vertically upward from the ground next to a building passes the bottom of a window 1.8 s after being tossed and passes the top of the window 0.20 s later. the window is 2.0 m high from top to bottom. what was the ball's initial velocity? the unit vector j^ is directed upward. how far is the bottom of the window from the launch position? how high does the ball rise above the launch position?

Calculate the amount of heat produced when 18000 coulombs of charge is transferred in one hour through a potential difference of 50v