You are driving a 2500 kg car at a constant speed of 14 m/s along an icy but straight level road. As you approach an intersection, the traffic light turns red. You slam on the brakes. The wheels lock, your tires begin skidding, and the car slides to a halt in a distance of 25 m. What is the coefficient of kinetic friction between your tires and the icy road?
We were already given the answer (.4), but I don't understand how to get there and would really like a step-by-step answer. :)
I think I'm definitely going about this problem the wrong way, but I figured you must find time taken to reach the distance of 25 m, then average acceleration (change in v/t). I came up with an answer of 6.26 m/s^2 this way (technically, it would be a negative number, I think). I then calculated the net force with the formula f = ma and got 15,652.95 N. Problem is, I don't have the applied force given like I'm used to in order to find the friction force...Basically, I'm stuck from there (although I know the normal force is 25000 because normal force = force by gravity = mg. I also know the equation force of friction = coefficient of friction x normal force. My knowledge basically ends there and hopefully yours begins. xD)
Thanks in advance!Would someone help me with this physics problem?We know the equation F=ma
The only force that is stopping the car is Friction
Force of Friction = uFn, where Fn is the weight of the car (m*gravity)
So we have Force of Friction = Force to stop the car
u*Fn=m*a ( u is the coefficient of friction, Fn is force normal, m is the mass of the car, and a is the acceleration of the car (which is slowing down))
u * m * g = m * a
First we need to calculate the acceleration of the car
V2^2 = V1^2 + 2 * a * d
(14m/s)^2 = 0^2 + 2 * a * 25m
a=3.92 m/s^2
now we have
u*m*g=m*a, it turns out we dont even need the mass of the car
u*g=a, u*9.81m/s^2 =3.92 m/s^2
u=3.92/9.81 = 0.39959 = 0.4Would someone help me with this physics problem?Well set f = ma = friction. I forget the formula for force due to friction, but go that way.Would someone help me with this physics problem?You got the acceleration wrong. It's 3.57s / 14 m/s
Then sum force and acceleration.
mu(k)*N = ma
N=mg
mu(k) = 0.39959 ~ 0.4
It turns out that the force of Friction is acting in the positive x direction because the vehicle is slowing.Would someone help me with this physics problem?Hey Renisca
All that went wrong was that you slipped up at the beginning. We don't want average deceleration we need the real thing!
To find it, use one of the equation of motion:
v^2 = u^2 + 2as
From there you get the correct value of a, and a coeffictiant of friction 渭 = ~0.4
