# Homework Help: Centripetal Force - Banked Curve

1. Oct 19, 2012

### Nicolaus

1. The problem statement, all variables and given/known data
A 1000kg car travels around a frictionless banked curve having a radius of 80m. If the banking is 20 degrees to the horizontal, at which specific speed must the car travel to maintain a constant radius?

2. Relevant equations
Fc = mv^2/r
Fg(perp.) = mgcos(20)

3. The attempt at a solution
Would someone explain to me why we use the perp instead of the parallel angle on the incline? Is it because the car is travelling in the straight (toward the plane) direction along the banked curve?

2. Oct 19, 2012

### voko

What do you mean by "parallel" and "perpendicular" angles?

3. Oct 19, 2012

### Nicolaus

I meant the force of gravity parallel and perp to the incline.

4. Oct 19, 2012

### voko

In the parallel and perpendicular coordinate axes, what is the reaction force and what is the acceleration?

5. Oct 19, 2012

### lep11

Here's a diagram I made. N_x=m*v^2/r and N_y-G=0
we get two equations
N*sin20=mv^2/r and
N*cos20=mg
Then solve for v.

#### Attached Files:

• ###### diagram.png
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Last edited: Oct 19, 2012
6. Oct 19, 2012

Thank you.