A lightly damped harmonic oscillator, with a damping force ...

[MirandaLo]

A lightly damped harmonic oscillator, with a damping force proportional to its speed, is oscillating with an amplitude of 0.500 cm at time t = 0. When t = 8.20 s, the amplitude has died down to 0.400 cm.
 
  At what value of t will the oscillations have an amplitude of 0.250 cm?
  A) 5.13 s B) 16.5 s C) 18.5 s D) 25.5 s E) 20.5 s

Question 2

Three point charges are placed on the x-axis. A charge of +2.0 C is placed at the origin, -2.0 C to the right at x = 50 cm, and +4.0 C at the 100 cm mark.
 
  What are the magnitude and direction of the electrostatic force that acts on the charge at the origin? (k = 1/40 = 8.99  109 N  m2/C2)

[mcabuhat]

Answer to Question 1

D

Answer to Question 2

0.072 N, toward the right

[MirandaLo]

Thanks for the timely response, appreciate it

[patma1981]

Excellent