# Homework Help: Find the Acceleration of the Aar Going Downhill

1. Nov 11, 2008

### Trix

1. The problem statement, all variables and given/known data
A car originally traveling at 30 m/s manages to break for 5 sec. while traveling 125 m downhill. At that point the breaks fail. After an additional 5 sec. it travels an additional 150 m down the hill. What was the acceleration of the car after the breaks failed?

2. Relevant equations
Vxf = Vxi + axt and solve for a,Xf - Xi = Vxit + (1/2)axt^2, or ax = (Vxf - Vxi)/t

3. The attempt at a solution
Well, I've tried to use all 3 equations to no avail, perhaps I'm using the wrong ones or I don't understand the question. Or maybe it wants the instantaneous acceleration at that instant (when breaks fail)? Any tips, suggestions are welcome, thanks.

2. Nov 11, 2008

### Redbelly98

Staff Emeritus
You'll need to apply those equations to two separate pieces of the car's motion, (1) with breaks on the first 5 sec and (2) with breaks off for the next 5 sec.