Question

A lifeguard standing by a pool observes a child in difficulty (Figure 2). The lifeguard runs at an
average speed vR along the edge of the pool for a distance x, then jumps into the pool and swims
with average speed vS in a straight path toward the child. a) Show that the total time t it takes
the lifeguard to reach the child is given by equation 1. Assume vR = 4.0m/s and vS = 1.5m/s.
Use a spreadsheet on Excel to plot t versus x from (a), and from this plot determine the optimal
distance x that the lifeguard should travel before jumping into the pool (i.e., find the value of x
1
that minimizes the time t to reach the child).
t =
x
vR
+
p
D2 + (d − x)
2
vS

Answer 1

Respuesta:

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