Which statement is true about AC? A. The electrons move back and forth. B. The +/– polarity is constant. C. It is most common in portable devices. D. It can produce only low voltages.

Matter is needed to transfer thermal energy bya. conductionb. convectionc. radiation d. both a & b.

The law of the conservation of momentum says that the total momentum of any closed and isolated system cannot

The experiment done in lab is repeated, using a ball that has unknown mass m. you plot your data in the form of f 2 versus m/l, with f in rev/s, m in kg, and l in m. your data falls close to a straight line that has slope 3.19 m/(kg · s2). use g = 9.80 m/s2 and calculate the mass m of the ball.