A swan on a lake gets airborne by flapping its wings and running on top of the water.
(a) If the swan must reach a velocity of 6.00 m/s to take off and it accelerates from rest at an average rate of 0.350 m/s2, how far will it travel before becoming airborne?
(b) How long does this take?
Solution:
Part A
We are given the following values: v_f=6.00\:\text{m/s}; v_0=0\:\text{m/s}; and a=0.350\:\text{m/s}^2.
From the kinematic equations, the most applicable formula to solve for the change in distance, \Delta \text{x}, is
\left(v_f\right)^2=\left(v_0\right)^2+2a\Delta x
Solving for \Delta \text{x} in terms of the other variables, we have
\Delta x=\frac{\left(v_f\right)^2-\left(v_0\right)^2}{2a}
Substituting the given values,
\begin{align*}
\Delta x & =\frac{\left(v_f\right)^2-\left(v_0\right)^2}{2a} \\
\Delta x & =\frac{\left(6.00\:\text{m/s}\right)^2-\left(0.00\:\text{m/s}\right)^2}{2\left(0.350\:\text{m/s}^2\right)} \\
\Delta x & =51.4286\:\text{m} \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)
\end{align*}
Part B
From the formula v_f=v_0+at, solve for time, t in terms of the other variables.
Substitute the given values
\begin{align*}
t & =\frac{v_f-v_0}{a} \\
t & =\frac{6.00\:\text{m/s}-0.00\:\text{m/s}}{0.350\:\text{m/s}^2} \\
t & =17.1429\:\text{s} \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)
\end{align*}
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