A 27.0-kg block is resting on a flat horizontal table. On top of this block is resting a 13.0-kg block, to which a horizontal spring is attached, as the drawing illustrates. The spring constant of the spring is 310 N/m. The coefficient of kinetic friction between the lower block and the table is 0.490, and the coefficient of static friction between the two blocks is 0.720. A horizontal force is applied to the lower block as shown. This force is increasing in such a way as to keep the blocks moving at a constant speed.
Determine the amount by which the spring is compressed at the point where the upper block begins to slip on the lower block.
i just don't know if the coefficients of friction will be pointing towards the wall or away
To determine the direction of the coefficients of friction in this problem, you need to consider the forces acting on each block separately.
Let's start with the lower block. Since it is resting on the table and the applied force is in the rightward direction, the direction of motion of the lower block will be to the right. According to Newton's third law, the frictional force will act in the opposite direction of the motion. Therefore, the coefficient of kinetic friction between the lower block and the table will be pointing towards the left.
Now let's consider the upper block. It is directly connected to the lower block and moves with it. Therefore, the upper block will also move to the right. Similarly, the frictional force between the two blocks will act in the opposite direction of the motion, which is towards the left. Hence, the coefficient of static friction between the two blocks will also be pointing towards the left.
In summary, both coefficients of friction will be pointing towards the left in this problem.