Directions: Select ALL the correct answers.

Friction is a force that can oppose the motion of two objects that are touching each other. Which of the following are examples of friction?

A. A nail holds two wooden boards together.
B. A parachute softens the landing of a skydiver.
C. A space probe orbits the Moon.
D. The brakes on a bike rub against the wheel.

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) =_