Physics
posted by Emma .
A car mass of 1330 kg is traveling at 28.0 m/s. The driver applies the brakes to bring the car to a rest over a distance of 79.0 m. Calculate the retarding force.

Vo = sqrt(2 a X)
Solve that for the acceleration, a.
X = the stopping distance, 79 m
a = Vo^2/(2X)= 4.96 m/s^2
Themn use F = M a 
Two men pull a 31kg box with forces 9.7 N and 7.6 N. Find the resultant scceleration of the box.

Please post new questions separately, using "Post a New Question"
Your question cannot be answered unless the directions of the two pulling forces are specified 
does "sqrt" mean square root?