Answer: -56494.12km/h2
Step-by-step explanation:
We use one of the equations of motion to answer this question, preferably for one that has all the parameters we've been given
v2-u2=2as
v=final speed = 0
u=initial speed = 85km/h
s=distance = 85m =0.085km
a=acceleration
Then we make a the subject of formula
a=(v2-u2)/2s
Inputting all our values
a = -56494.12km/h2
the negative sign shows that it's decelerating
So therefore
deceleration = 56494km/h2
The workings is in the picture I sent
