Friction Force of a rubber ball

[I <3 Physic]

Homework Statement

If a 2.5 kg rubber ball is rolled across the dry concrete floor with an acceleration of 4.0 m/s^2[E]. Determine the friction force required to stop the ball. (Drawing a free body diagram will help illustrate this situation)

Homework Equations

Fk= µk(Fn)
F=ma

The Attempt at a Solution

a=4.0 m/s^2[E]

m=2.5kg
µk= 1Find Fn=mg

=2.5(9.81)

=24.5

Find friction force to stop the ballFk=1(24.5)

Fk=24.5

Find Fnet=ma

=2.5(4.0)

=10 N(E)
These numbers are telling me that the object should not be moving in the first place? Which is confusing because i am given an acceleration

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[RUber]

Why did you set $\mu k = 1$?

 

[I <3 Physic]

that was the value that was given to me, on my coefficients of friction sheet.

 

[462chevelle]

That is very high, that is a friction i would expect to be static. and i thought rubber to concrete was somewhere around .8 mus