Doc Brown has calculated his Delorean can accelerate at a rate of 2.52 m/s/s. How far away must he and Marty stand to allow the car to accelerate from rest to a speed
of 39.2 m/s?

304.89m

Explanation:

Given

acceleration a = 2.52m/s²

final speed v = 39.2m/s

initial speed = 0m/s (car accelerates from rest)

Using the equation of motion below to get the distance of Doc brown from Marty;

v² = u²+2as

substitute the given parameters

39.2² = 0²+2(2.52)s

1536.64 = 0+5.04s

divide both sides by 5.04

1536.64/5.04 = 5.04s/5.04

rearrange the equation

5.04s/5.04 = 1536.64/5.04

s = 304.89m

Hence He and Marty must stand at 304.89m to allow the car to accelerate from rest to a speed  of 39.2 m/s?

it doesn't. it was imagined up in the middle ages.