We can use the kinematics equation
v1^2-v0^2=2as
where v1=final velocity = 0 m/s
v0=initial velocity = 24 m/s
a=acceleration = to be determined
S=distance travelled during acceleration = 225 m
=>
a=(v1^2-v0^2)/(2S)
=(0^2-24^2)/(2*225)
=-576/450
=-1.28 m/s^2
So van is decelerating at 1.28 m/s^2
The frictional force is therefore
F = ma = 1400 kg * 1.28 m/s^2 = 1792 N
