Question

2 mark for review a wooden block is initially traveling upward along a rough inclined surface, as shown in figure 1. the block continues to travel up the incline a short distance, and then reverses direction and travels down the incline as shown in figure 2. which of the following pairs of free - body diagrams best represents the forces exerted on the block while it is traveling up the incline and traveling down the incline?

Explanation:

Step1: Analyze forces when moving up - incline

When the block is moving up the incline, the gravitational force $mg$ acts down - ward. The normal force $N$ acts perpendicular to the incline surface. The frictional force $f$ acts down - the incline because it opposes the motion of the block, so $f=\mu N$ where $\mu$ is the coefficient of friction.

Step2: Analyze forces when moving down - incline

When the block is moving down the incline, the gravitational force $mg$ still acts downward. The normal force $N$ still acts perpendicular to the incline surface. The frictional force $f$ now acts up - the incline as it opposes the motion of the block.

Answer:

When moving up the incline: gravitational force ($mg$) downward, normal force ($N$) perpendicular to the incline, frictional force ($f$) down - the incline. When moving down the incline: gravitational force ($mg$) downward, normal force ($N$) perpendicular to the incline, frictional force ($f$) up - the incline.