To analyze the situation with blocks A and B, we need to consider the forces acting on both blocks and how they interact with each other. Since block B is being pushed with a force of 20 N to the right and both blocks are moving with a constant velocity of 10 m/s, we can deduce some important details about the frictional forces at play.
Understanding the Forces Involved
First, let's break down the forces acting on block B. When a force is applied to block B, it experiences both the applied force and the frictional force acting against it. The frictional force is what allows block A to stay on top of block B without slipping off.
Applying Newton's Laws
According to Newton's first law, an object in motion will remain in motion at a constant velocity unless acted upon by a net external force. Since the blocks are moving at a constant velocity, the net force acting on block B must be zero. This means that the applied force of 20 N is balanced by the frictional force exerted by block A on block B.
Calculating the Frictional Force
Let’s denote the frictional force exerted by block A on block B as \( F_f \). Since the system is moving at a constant velocity, we can set up the following equation:
- Applied Force (20 N) = Frictional Force (\( F_f \))
From this, we can conclude that:
- \( F_f = 20 \, \text{N} \)
This means that the frictional force applied by block B on block A is also 20 N, acting to the left, opposing the motion of block B.
Role of Friction
The rough surfaces in contact between blocks A and B are crucial for this interaction. The frictional force is what prevents block A from sliding off block B as it moves. If the frictional force were less than 20 N, block A would start to slip off block B. Therefore, the roughness of the surfaces ensures that the frictional force is sufficient to keep both blocks moving together.
Conclusion on Frictional Forces
In summary, the frictional force exerted by block B on block A is 20 N to the left, which balances the applied force of 20 N to the right. This balance allows both blocks to move together at a constant velocity of 10 m/s. Understanding these forces helps us appreciate the role of friction in everyday situations, such as how vehicles maintain traction on the road or how objects can be stacked without falling.
