A uniform plank of length L leans against a vertical wall, its head a distance h above the horizontal ground. If we let go of the plank from rest, how far above the ground is the head of the plank the moment it loses contact with the wall?

A current of 1.03 A flows in a wire. How many electrons are flowing past any point in the wire per second? The charge on one electron is 1.60 10-19 C