American power plants usually supply 120 V ac.
(a) At what frequency is this voltage supplied?
(b) What is the maximum voltage?
Question 2
A galaxy is observed receding from Earth with a speed of 2800 km/s.
If the Hubble constant is 22 km/s per million light-years, estimate how many years ago the light that we presently see from the galaxy actually left the galaxy. (c = 3.00 108 m/s, 1 ly = 9.461 1015 m, 1 y = 3.156 107 s)
A) 1.4 107 y B) 4.2 107 y C) 4.2 108 y D) 4.2 106 y E) 1.3 108 y