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Worksheet Riemann Sums

1.

Suppose that an object moving along a straight line path has its velocity in feet per second at time \(t\) in seconds given by \(v(t) = \frac{2}{9}(t-3)^2 + 2\text{.}\)

(a)

Carefully sketch the region whose exact area will tell you the value of the distance the object traveled on the time interval \(2 \le t \le 5\text{.}\)

(b)

Estimate the distance traveled on \([2,5]\) by computing \(L_4\text{,}\) \(R_4\text{,}\) and \(M_4\text{.}\)

(c)

Does averaging \(L_4\) and \(R_4\) result in the same value as \(M_4\text{?}\) If not, what do you think the average of \(L_4\) and \(R_4\) measures?

2.

Suppose that an object moving along a straight line path has its velocity \(v\) (in feet per second) at time \(t\) (in seconds) given by
\begin{equation*} v(t) = \frac{1}{2}t^2 - 3t + \frac{7}{2}\text{.} \end{equation*}

(a)

Compute \(M_5\text{,}\) the middle Riemann sum, for \(v\) on the time interval \([1,5]\text{.}\) Be sure to clearly identify the value of \(\Delta t\) as well as the locations of \(t_0\text{,}\) \(t_1\text{,}\) \(\cdots\text{,}\) \(t_5\text{.}\) In addition, provide a careful sketch of the function and the corresponding rectangles that are being used in the sum.

(b)

Give an estimate for the total change in position of the object on the interval \([1,5]\text{.}\)

(c)

Give an estimate for the total distance traveled by the object on \([1,5]\text{.}\)

(d)

Use appropriate computing technology such as this applet to compute \(M_{10}\) and \(M_{20}\text{.}\) What exact value do you think the middle sum eventually approaches as \(n\) increases without bound? What does that number represent in the physical context of the overall problem?