Answered By Daniel A

Hey, there. I don't have all the context around this question but I'll do my best to fill in the blanks.

So, I'm assuming that a force meter is attached to this toboggan, a pulling force is applied, and the force in question here is static friction. As you pull on the toboggan, the static friction will increase steadily as it matches the pulling force you apply, until it reaches a maximum. This point is determined by the weight of the toboggan and the coefficients of friction of its material and the material that it is sliding on. Once the pulling force exceeds the maximal force of static friction, the net force acting on the toboggan will no longer be zero and, as dictated by Newton's first law of motion, it will begin to move in the direction of the pulling force.

 

Hope this clears things up for you :)