Alice is driving down the road at 86 m/s when she sees a speed limit sign for 7m/s. what is
the magnitude of her average acceleration if it takes her 8s to slow down?

Explanation:

Acceleration,

Where v and u are the final and initial velocities of Alice's car respectively, t is the time taken for Alice's car to attain velocity of 7 m/s.

Substituting 7 m/s for v, 86 m/s for u and 8 s for t then

Therefore, the car decelerates at a rate of

r = ρ x length / area  

ρ = r x area / length  

ρ is in ohm-meters  

in basic units, it is m³kg/s³a²  

i think this is it.