In the periodic table of elements, what do all the elements 2 in a row have in common

Which radioisotope is used in dating geological formations?

A47 kg person in a rollercoaster moving through the bottom of a curved track of radius 47.7 m feels a normal force of 895 n. what is the net centripedal force acting on the person

Working alone at its constant rate, pump x pumped out ¼ of the water in a tank in 2 hours. then pumps y and z started working and the three pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 3 hours. if pump y, working alone at its constant rate, would have taken 18 hours to pump out the rest of the water, how many hours would it have taken pump z, working alone at its constant rate, to pump out all of the water that was pumped out of the tank? a) 6b) 12c) 15d) 18e) 24