Answer
The force of friction acting on the suitcase is $12.5~N$
Work Step by Step
Since the suitcase is moving at a constant speed, the force of friction $F_f$ is equal in magnitude to the horizontal component of the applied force $F$. We can find the force of friction:
$F_f = F~sin~\theta$
$F_f = (25.0~N)~sin~30.0^{\circ}$
$F_f = 12.5~N$
The force of friction acting on the suitcase is $12.5~N$
