# Homework Help: Uniform circular motion (I DON'T KNOW)

1. Oct 31, 2005

### heelp

WHAT IS THE MAXIMUM SPEED WITH WHICH A 1050KG CAR CAN ROUND A TURN OF RADIUS 77M ON A FLAT ROAD IF THE COESFFIECENT OF STATIC FRICTION BETWEEN TIRES AND ROAD IS .80? here is what I have so far?

m= 1050kg
r =77m
uk =.080
FN=mg FR =ukfn
(1050kg)(9.8m/s) = FN = 10290N
(.80) (10290) = 8232N= FR
A= F/m a=10290N + 8232N/1050 17.64M/S^2
SPEED = X/T 77/17.64 =4.4m/s
Not sure am I right?

2. Oct 31, 2005

### newcool

At max speed:
F_s = ma
F_s = u_s * N = u_s*mg

Remember that a = v^2/r and solve for v.

3. Oct 31, 2005

### heelp

v= squre root of (9.8m/s^2)(77m) = is the maxium speed 27.46m/s

Last edited: Oct 31, 2005
4. Oct 31, 2005

### newcool

You don't need to know time.

F_s = ma

You know F_s, you know m and you know that a = v^2/r

5. Oct 31, 2005

### ranger

[
Why did you use acceleration = 9.80 m/s/s ?
The car is on a flat surface with acceleration directed along the x-axis. This causes the car to move forward. Force of gravity acts on the y-axis pulling an object downward.

http://www.physicsclassroom.com/Class/circles/U6L2a.html

Last edited: Oct 31, 2005
6. Oct 31, 2005

### heelp

is F_S IS TOTAL Force

7. Oct 31, 2005

### ranger

Fnet is simply the sum of all the forces.