- #1
wtfcat
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Homework Statement
If a car's wheels are locked during emergency braking, the car slides along the road. The record for the longest skid marks on a road was reportedly set in 1960. the marks were 290m long. assuming that [tex]\mu[/tex] = 0.6, how fast was the car going when the wheels became locked?
Givens:
Vf = 0m/s
Vi = ?
d = 290m
a = ?
[tex]\mu[/tex] = 0.6
g = 9.8m/s2
Formulas:
[tex]\Sigma[/tex]F = ma
[tex]\mu[/tex]k = Fk/Fn
Vf2 = Vi2 + 2ad
Homework Equations
1. Am i missing anything? Givens, formulas, etc.
2. Are my steps correct? ex. in my steps, am i missing a positive or negative sign, did i get units right, etc
3. Is my answer correct?
The Attempt at a Solution
So in this case, [tex]\Sigma[/tex]F = Fk, correct? And Fk = [tex]\mu[/tex]kmg, so ma = [tex]\mu[/tex]kmg, and cancelling out the m gives me a = [tex]\mu[/tex]kg. so a = (0.6)(9.8) = 5.88m/s2.
i sub "a" into the kinematic equation: Vf2 = Vi2 + 2ad ---> 0 = Vi2 + 2(5.88)(290) ---> -Vi2 = 3410.4 ---> -Vi = 58.3986m/s
If it's negative Vi, then does that mean that it was going backwards or something, or am i missing something here? Thanks in advance for taking the time to help me out!