Homework Help: Physics

Posted by Lena on Friday, April 17, 2009 at 12:39am.

You are driving 2500 Kg car at a constant speed of 14 m/s along an icy, but stright and lvel road. While approaching a traffic light, it turns red. You slam on the brakes. You wheels lock, the tires begin skidding and the car slides to a halt in a distance of 25 m. What is the coefficient of sliding friction between the tires and the icy road?

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Calculations:

m = 2500 Kg
Vi = 14 m/s
Vf = 0 m/s
deltaD = 25 m
a = (vf^2 - vi^2)/(2 x deltaD)
= -14 m/s / 50
= 2.8 m/s^2

W = (2500) (9.81)
= 24525 N

Fnet = (2500)(-0.28)
= -700 N

I`m not sure what to do after this.

Physics - drwls, Friday, April 17, 2009 at 1:53am
(friction force) x (distance of skid) = Kinetic energy loss
Use that equation to get the friction force, f.
The coefficient of kinetic friction, Uk, can be obtained from
Uk = f/(M*g)
Physics - Lena, Friday, April 17, 2009 at 2:03am
oh ok thanks :)
Physics - aadi, Monday, December 13, 2010 at 2:14am
dont forget its 14^2/50 - -3.92m/s^2

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