Need find end velocity given accel., time, distance

  • #1
urgent!! Need find end velocity given accel., time, distance

1.The driver of a car slams on the brakes when he sees a tree blocking the road. The car slows with a constant acceleration -5.90 m/s2 for 4.45 s, making straight skid marks 60.0 m long ending at the tree. With what speed does the car then strike the tree?


The Attempt at a Solution



so I tried to find Vo using Vo=x-at^2/2
and I plugged Vo into Vf=Vi+at and got 13.4 but it was wrong.
Please help me I am so confused.
 

Answers and Replies

  • #2
nasu
Gold Member
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1.The driver of a car slams on the brakes when he sees a tree blocking the road. The car slows with a constant acceleration -5.90 m/s2 for 4.45 s, making straight skid marks 60.0 m long ending at the tree. With what speed does the car then strike the tree?


The Attempt at a Solution



so I tried to find Vo using Vo=x-at^2/2
and I plugged Vo into Vf=Vi+at and got 13.4 but it was wrong.
Please help me I am so confused.


The equation in red is wrong. See again the equation of motion (for position vs time).
The idea of using the two equations to eliminate vo is OK.
 

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