If two stacked blocks are moving with a constant speed, it means that the net force acting on the system is zero. This situation does not violate Newton's second law but rather demonstrates a balance of forces.
Newton's second law states that the net force acting on an object is equal to the mass of the object multiplied by its acceleration:
F_net = m * a
When the velocity of the stacked blocks remains constant, it implies that the acceleration is zero (since acceleration is the rate of change of velocity). Therefore, the net force on the system must also be zero.
In the case of the stacked blocks, there could be opposing forces at play that balance each other out. For example, if a force is applied to push the blocks to the right, there could be an equal and opposite frictional force acting to the left. As a result, the net force is zero, and the blocks continue to move with a constant speed.
It's important to note that even though the net force is zero, there can still be individual forces acting on the blocks. The forces simply cancel each other out, resulting in no net force and constant speed.
So, the situation where the stacked blocks move with a constant speed does not violate the second law of Newton but rather demonstrates the concept of balanced forces.