Two boxes are connected by a string. The first box has a mass of 4.2 kg and the second 2.8 kg. A string attached to the first box pulls horizontally with a force of
7.5 N. Calculate the tension in the second string if the force of friction on the first
box is 2.0 N and the force of friction on the second is 1.6 N.

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) =_