Which sentence correctly describes a friction force? a. it acts in the same direction as the motion of an object. b. it acts in a direction opposite to the motion of an object. c. it acts in the same direction as the force of gravity on an object. d. it acts in a direction perpendicular to the motion of an object.

In the circuit, the switch s has been open for a long time and r = 125 kohm. it is then suddenly closed. (a) determine the time constant before the switch is closed. s (b) determine the time constant after the switch is closed. _ s (c) let the switch be closed at t = 0. find the current in the switch as a function of time. (use t for time. express your answer in milliamps and seconds.) i(t) =_