Finding speed when given deceleration and distance?

[Mady Hernandez]

Hi!
I have this homework problem that has me completely stumped. Any help is greatly appreciated!

In coming to a stop, a car leaves skid marks 80m long on the highway. Assuming a deceleration of 7.00m/s², estimate the speed of the car just before braking.

I just can't figure out what formula to use. If you can help, thank you so much!

 

[scottdave]

Look up Equations of Motion or SUVAT. Here is one link. https://en.wikipedia.org/wiki/Equations_of_motion

 

[Albertxxx]

Hi!
I have this homework problem that has me completely stumped. Any help is greatly appreciated!

In coming to a stop, a car leaves skid marks 80m long on the highway. Assuming a deceleration of 7.00m/s², estimate the speed of the car just before braking.

I just can't figure out what formula to use. If you can help, thank you so much!

You can solve it using v^2 -u^2=2as.
Since you decelerating, put in a=-7.
You need to find u here