Answer:
1.40 N
Explanation:
The magnitude of the frictional force is given by:
[tex]F=\mu N[/tex]
where
[tex]\mu[/tex] is the coefficient of friction
N is the magnitude of the normal reaction
The coefficient of friction for this problem is [tex]\mu=0.012[/tex]. The magnitude of the normal reaction is equal to the combined weight of the boy and the sled, because the surface is horizontal, so
[tex]N=65 N+52 N=117 N[/tex]
Therefore, the frictional force is
[tex]F=\mu N=(0.012)(117 N)=1.40 N[/tex]
