You're designing a highway so that the maximum centripetal acceleration on a curve is no more than

$1\mathrm{.}50$ m$/$s$2.$ What is the minimum curvature radius to accommodate a $1\mathrm{.}20$ x $102$ km$/$h maximum speed?

$9.$ A fire truck approaches and passes you at constant speed. If the siren frequency you hear drops from

an initial $692.$ Hz $($approaching$)$ to a final $615.$ Hz $($receding$),$ what's the truck's speed? The speed of

sound is $343.$ m$/$s$.$

$10.$ A piston oscillates vertically at $7\mathrm{.}50$ Hz$.$ Find the maximum oscillation amplitude so a coin resting atop

the piston doesn't come off at any point in the cycle.