We can use the equation of motion, `v^2 = u^2 + 2as`
where u is the initial velocity of the object, v is the final velocity of the object, s is the distance traveled and a is the acceleration.
In this case, the initial velocity of the car is 10 m/s and it travels for 8 m.
Thus, u = 10 m/s and s = 8 m
Since the car stops, v = 0
Substituting these values, we get
`0 = 10^2 + 2a(8)`
Solving this equation, we get, a = - 6.25 m/s^2 (negative sign indicates deceleration).
Using Newton's Second Law of Motion, force is related to mass and acceleration of an object as F = ma.
Here, the mass of the car m = 800 kg
Thus, the average force exerted by the brakes = ma = 800 x 6.25 = 5,000 N.
Hope this helps.