- #1
shizupple
- 20
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Homework Statement
A car starts from rest and travels for 5.5 s with a uniform acceleration of +1.4 m/s2. The driver then applies the brakes, causing a uniform acceleration of -1.9 m/s2. The breaks are applied for 1.70 s.
(a) How fast is the car going at the end of the braking period?
4.47 m/s (I got this part)
(b) How far has the car gone from its start?
? m
Homework Equations
1) V=Vi + at
2) x=Vit + 1/2at^2
3) V^2=Vi^2 + 2ax
4) a=V/t
5) v=x/t
The Attempt at a Solution
Vf^2=Vi^2+2a(x)
4.47^2=7.7^2+2(1.4)(x)
-14.04=X
I know this obviously can't be the answer. I'm just confused as to how to do this because there is two different accelerations. Do i find the avg acceleration by adding them up and dividing by two or do i find the displacement before braking then subtract the displacement after braking? I'm not sure which formula to use?