How to Find Acceleration for a Car Stopping Over 50m from 80 km/h?

[888]

hi,
i need help on a question... if a car stop in a distance of 50m from the speed of 80 km/h how do you find the acceleration is m/s/s? thanks

 

[Kurdt]

What equations of motion do you know? How about rearanging:

$$v^2=u^2 + 2as$$

 

[888]

i've never used that equation before but all the other equations i know are for constant acceleration or average velocity

 

[d_leet]

i've never used that equation before but all the other equations i know are for constant acceleration or average velocity

Well what equations do you know?

 

[Kurdt]

The equation I put up was for constant acceleration and speeds.

 

[888]

the equations that i know are: aver. v= v2+v1/2
x2= x1+v1t+.5at^2
v^2=V1^2+2a(x2-x1)
v2= v1+at
those are only for constant acc.

aver acc= v2-v1/t2-t1
aver. vel.=x2-x1/t2-t1

 

[d_leet]

v^2=V1^2+2a(x2-x1)

This is the same equation as Kurdt posted above, and it is the one that you should use to solve this problem.

 

[Integral]

Thats just fine because you are looking for the constant acceleration.

 

[888]

however the question doesn't say it's looking for constant acceleration

 

[d_leet]

however the question doesn't say it's looking for constant acceleration

But it does say to find the acceleration, and unless you know how to find a non-constant acceleration you should just assume that you are looking for constant acceleration.