# Homework Help: Circular Velocity of car

1. Sep 26, 2011

### JayHakimi1

1. The problem statement, all variables and given/known data
Disturbed by speeding cars outside his workplace, Nobel laureate Arthur Holly Compton designed a speed bump (called the "Holly hump") and had it installed. Suppose a 1 800-kg car passes over a hump in a roadway that follows the arc of a circle of radius 21.4 m as in the figure below.

(a) If the car travels at 28.5 km/h what force does the road exert on the car as the car passes the highest point of the hump?

2. Relevant equations

Normal Force - Weight = [mass(velocity^2)]/radius

3. The attempt at a solution

I used the equation above and converted the velocity to m/s which i got 7.9166

Then basically plug n chug.

My final answer was 22911.6 (sig figs doesn't matter here)

But when I submitted my answer it says my answer is off more than %10 of the actual answer.

Any suggestions?

2. Sep 26, 2011

### danielakkerma

Hi,
You should've included the centrifugle force, in your reference frame, in the following manner:
$\large N-mg+F_c = 0 \Longrightarrow N = mg-\frac{mv^2}{R}$
Try it,
Daniel