# physics

posted by
**puff puff** on
.

A curve of radius 60m is banked so that a car traveling with uniform speed 70km/hr can round the curve without relying on friction to keep it from slipping to its left or right. The acceleration of gravity is 9.8m/s^2. What the the Angle of the curve?

im using a=v^2/r, but when I get the acceleration, I don't know what to do no more.. Can anyone help me on this one? Thanks a bunch!

You do not have to rely of friction to keep the car from slipping if the road is banked at an angle such that the force applied by the road to the tires is perpendicular to the surface of the road. The horizontal component of that force, in that situation, equals the centripetal acceleration M V^2/R and the vertical component balances the weight, M g.

By drawing yourself a figure, you should be able to convince yourself that the "bank angle" of the curve is

theta = arctan [(MV^2/R)/Mg]

= arctan [V^2/(R g)]

Make sure you express V in m/s when using the formula.