Answer
(a) 51 revolutions.
(b) $8.7~ft$
Work Step by Step
See conversion factors (inside front cover).
$1~yd=3~ft$, $1~ft=30.5~cm$
(a) $time=\frac{distance}{speed}=\frac{150~yd}{31~cm/s}(\frac{3~ft}{1~yd})(\frac{30.5~cm}{1~ft})(\frac{1~min}{60~s})=7.38~min$
Let N be the number of revolutions.
$N=(7~revolutions/min)(7.38~min)=51.7$.
That is, 51 revolutions completed plus 0.7 of a revolution.
(b) $distance=(speed)(time)$
$distance=(31~cm/s)(\frac{1~revolution}{7~revolutions/min})(\frac{60~s}{1~min})(\frac{1~ft}{30.5~cm})=8.7~ft$
