The frictional force must also be 10N to keep the velocity constant.
F = uN
where F is the frictional force, u is the coefficient of friction, and N is the normal contact force.
The normal contact force is equal to the body's weight in this situation as it is the only vertical force acting down.
So F = umg
Where m is the mass of the body and g is the acceleration due to gravity
Rearrange for u:
u = F/mg
Sub in values:
u = 10/(10•9.8)
u = 1/9.8 = 0.10 (to 2.s.f)