help on Physics Angles?

[rai j]

You are asked to design a new freeway off ramp for Popular Avenue. Suppose the new
ramp is to have a radius of 125 meters. What angle should the roadway be banked for a
exit speed of 45 mi/hr


i have no idea how to do this. please help me.
any help at all is appreciated thank you!

[Pearlsawme]

If ? is the angle of banking,
the normal reaction N of the road is inclined at angle ?
to the vertical.
Its horizontal component provides the centripetal force mv^2 /r.
N sin ? = mv^2 /r.--------------------1.
Its vertical component balances the weight of the car.
N cos ? = m g .--------------------2
1 divided by 2 gives
tan ? = v^2 / ( r g }
=============================

45 m/ h = 45*1609 m /hour = 20.11 m/s.

tan ? = 20.11 ^2 / ( 125*9.8 }

? = 18.27?
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