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## Homework Statement

A car is on a banked curve of bank angle 18 deg, radius 70m. It's mass is 1020kg. Draw a free body force diagram approximately to scale, when the car is at the 'design speed'. What is meant by design speed? Find the resultant force and the normal force n.

## Homework Equations

*n*cos[tex]\theta[/tex] =

*mg*

Design speed = Speed at which a car no longer relies on friction in order to keep from sliding down the bank.

## The Attempt at a Solution

To find the normal force, I think I am supposed to use the equation

*n*cos[tex]\theta[/tex] =

*mg*, or solving for n: n = mg / cos[tex]\theta[/tex]. Plugging in the values I get n = 1020kg x 9.81/ cos18, thus n = 10521 N. Is this correct? I'm poor with trig functions, so I'm not sure how or why cos relates to this equation. If someone could explain this that would be great, as I'm truly trying to understand this material.

Would the resultant force be = 0? If the car is at a constant "design speed", it is not accelerating, thus no net force.