Capacitor, Charge, and Sinewave, please

[Chas3down]

Homework Statement

A capacitor C is charged to an initial potential of 70.0 V, with an initial charge of Q0. It is in a circuit with a switch and an inductor with inductance L = 4.03×10-2 H and resistance RL.

At t=0, the switch is closed, and the curve below shows the potential V across the capacitor as a function of time t.

https://s4.lite.msu.edu/cgi-bin/plot.png?file=jonesb63_msu_1427749730_13825679_plot.data

Calculate the energy in the circuit after a time of 16 periods. Note that the curve passes through a grid intersection point.

Calculate the time required for 86% of the initial energy to be dissipated.

The Attempt at a Solution

Not sure what is wrong with this.

 

[phyzguy]

I haven't looked through everything, but your calculation of the period is clearly incorrect. The sine wave passes through zero at t=0.7ms, but it is not zero at t=0. So the time between t=0 and t=0.7 is not a whole number of periods.

 

[Chas3down]

I haven't looked through everything, but your calculation of the period is clearly incorrect. The sine wave passes through zero at t=0.7ms, but it is not zero at t=0. So the time between t=0 and t=0.7 is not a whole number of periods.

oh 12.5 per second yeah my bad, thanks