# Exponential Damping 1#

A $${{params.m}}$$ kg mass oscillates on a $${{params.k}}$$ N/m spring. The damping constant of this spring is $$b$$ = $${{params.b}}$$ kg/s.

## Useful Info#

For slowly moving objects we’ve seen that the drag force grows in proportion to the velocity, $$\overrightarrow{D} = -b\overrightarrow{v}$$, where $$b$$ is the damping constant and $$\overrightarrow{v}$$ is the velocity of the object.

The net force acting on a slowly moving mass attached to a massless spring in the presence of a drag force (for motion along $$x$$ relative to an equilibrium point $$x_0$$) can be written as:

(9)#$$$F\_{net,x} = -b\frac{dx}{dt} - kx=ma = m\frac{d^2x}{dt^2}.$$$

The solution of this differential equation is found to be $$x(t) = Ae^{-\frac{bt}{2m}} \cos(\omega t) = Ae^{-\frac{t}{2\tau}} \cos(\omega t)= A(t) \cos(\omega t),$$ where $$A$$ is the initial amplitude of the oscillation, $$\tau$$ is the time constant, $$A(t)$$ is the time-dependent amplitude of the oscillation, and $$\omega = \sqrt{\frac{k}{m} - \frac{b^2}{4m^2}}$$ is the angular frequency of the damped oscillation.

## Part 1#

Find the time constant, $$\tau$$, of this spring.