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:

The solution of this differential equation is found to be \begin{equation} x(t) = Ae^{-\frac{bt}{2m}} \cos(\omega t) = Ae^{-\frac{t}{2\tau}} \cos(\omega t)= A(t) \cos(\omega t), \end{equation} 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.

Attribution#

Problem is licensed under the CC-BY-NC-SA 4.0 license.