3. A roller-coaster car is moving over the top of a hill. At the instant it is on the hill top, it has a kinetic energy of E and a gravitational potential energy of 3E. When it coasts down to ground level, if total mechanical energy is conserved, what is the kinetic energy of the car on the ground?
(A) 4E (B) 3E (C) 2E (D) E

You have a resistor and a capacitor of unknown values. first, you charge the capacitor and discharge it through the resistor. by monitoring the capacitor voltage on an oscilloscope, you see that the voltage decays to half its initial value in 3.00 ms . you then use the resistor and capacitor to make a low-pass filter. what is the crossover frequency fc?