# Travelling Wave Displacement#

$$D(x,t) = {{ params.A }}\cos({{ params.k }}x+ {{ params.omega }}t)$$ describes the displacement $$D$$ in $$\rm{cm}$$ of a travelling sinusoidal wave as a function of displacement $$x$$ in $$\rm{cm}$$ and time $$t$$ in $$\rm{s}$$.

## Part 1#

What is the amplitude $$A$$ of the travelling wave?

Please enter in a numeric value in $$\rm{cm}$$.

## Part 2#

In what direction is the travelling wave moving?

• {â€˜valueâ€™: â€˜The positive x direction.â€™, â€˜feedbackâ€™: â€˜Try setting the phase equal to a constant and differentiating the phase implicitly with respect to time. What is the sign of $$v = v_{x} = \\frac{dx}{dt}$$ ?â€™}

• {â€˜valueâ€™: â€˜The negative x direction.â€™, â€˜feedbackâ€™: â€˜Yes, you can see this by setting the phase equal to a constant and differentiating the phase implicitly with respect to time to find that $$v = v_{x} = \\frac{dx}{dt}$$ is negative.â€™}

## Part 3#

At what speed $$v$$ is the travelling wave moving?

Please enter in a numeric value in $$\rm{m/s}$$.