Question

A reconnaissance plane flies 556 km away from
its base at 832 m/s, then flies back to its base
at 1248 m/s.
What is its average speed?
Answer in units of m/s

Answer 1

We use the formula, to calculate the average speed of the round trip,

$v_{av} =\frac{d_{total}}{t_{total}}$

Here, $d_{total}$, is total distance covered by plane in total time, $t_{total}$.

For the round trip,

$d_{total=556\ km+556\ km=1112 \times 10^3\ m$

$t_{total}=\frac{556 \times 10^3 m}{832 m/s} + \frac{556 \times 10^3 m}{1248 m/s}$.

Thus,

$v_{av} =\frac{1112 \times 10^3\ m}{\frac{556 \times 10^3 m}{832 m/s} + \frac{556 \times 10^3 m}{1248 m/s}} =\frac{1112 \times 10^3\ m}{668.26\ s+445.51\s} \\\\v_{av}=998.41\ m/s$.