# Banked Curves - Question

1. Jan 12, 2006

### Xylitol

A curve of radius 170 m is banked at an angle of 22°. At what speed can it be negotiated under icy conditions where friction is negligible?

Can someone explain how to get the answer for this question? Thanks

2. Jan 12, 2006

### andrewchang

it concerns centripetal acceleration. did you try it at all? you need to at least show some of your work or thought processes.

3. Jan 12, 2006

### Xylitol

Ok
I drew out the FBD

Fg going down
Fny going up
Fnx going to the right
Fn going at a 68 degree angle to the horizontal

Using the trig functions, I got: (not to significant figures)
Fg = 9.8 [N]
Fn = 9.8 [N]
Fnx = 3.96 [N]
Fn = 10.57 [N]

Ac = (Vc^2)/(r)
Fc = MAc = (MVc^2)/(r)

4. Jan 12, 2006

### lightgrav

this is for your "1 kg" car, right?

which of these Forces is center-pointing?

5. Jan 12, 2006

### Xylitol

Fnx is center pointing

The mass is not given
Apparently the masses should cancel out with teh formulas but I dont really know which ones to choose

6. Jan 12, 2006

### robphy

What does Fc mean? That is to say, in your last equation, what is the meaning of Fc by itself, making no reference to the rest of the equalities on that line?

Hint: how does Fc relate to your FBD?

7. Jan 12, 2006

### Xylitol

Its going towards the center

8. Jan 13, 2006

### robphy

Why does one draw a FBD in the first place?
How does it help you correctly apply Newton-II? In fact, what is the precise statement of Newton-II?

9. Jan 13, 2006

### Xylitol

Netforce(X/Y) = MA