A total charge Q is uniformly distributed on a thread of length l. The thread forms a semicircle. What is the potential at the center? (Assume V=0 at large distances.) Express your answer in terms of the variables Q, l, and appropriate constants.

An engineer designs a roller coaster so that a car travels horizontally for 162 ft, then climbs 127 ft at an angle of 31.0° above the horizontal. it then moves 127 ft at an angle of 46.0° below the horizontal. if we take the initial horizontal motion of the car to be along the +x-axis, what is the car's displacement? (give the magnitude of your answer, in ft, to at least four significant figures and give the direction of your answer in degrees counterclockwise from the +x-axis.)

How many atoms of nitrogen are in the chemical formula ni(w on

By what primary heat transfer mechanism does the sun warm the earth?