Answer:
0.097
Explanation:
The sled is moving at constant velocity. This means that the acceleration is zero: a=0, so according to Newton's second law:
[tex]\sum F = ma[/tex]
where m is the combined mass of the sled and your friend, the resultant of the forces along the horizontal direction (the direction we are interested in) must be zero:
[tex]\sum F=0[/tex] (1)
There are only two forces acting along the horizontal direction:
[tex]F cos \theta[/tex] is the horizontal force you are applying to pull the sled, with F = 79 N and [tex]\theta=25^{\circ}[/tex]
[tex]F=-\mu mg[/tex] is the frictional force, with [tex]\mu[/tex] being the coefficient of friction, m = 75 kg the mass, and g = 9.8 m/s^2 the acceleration due to gravity. The negative sign is due to the fact that the friction is opposite to the pull applied.
Substituting into (1), we can find [tex]\mu[/tex]:
[tex]F cos \theta - \mu mg =0\\\mu = \frac{F cos \theta}{mg}=\frac{(79 N)(cos 25^{\circ})}{(75 kg)(9.8 m/s^2)}=0.097[/tex]
