The condition of the law of conservation of mechanical energy A piece of wood slides down a smooth slope. Because only gravity does work, the mechanical energy of the piece is conserved If the inclined plane is not smooth and the block is subject to friction, and a force F is applied to the block in the opposite direction and equal to the friction force, then can the mechanical energy of the block be considered to be conserved?

The condition of the law of conservation of mechanical energy A piece of wood slides down a smooth slope. Because only gravity does work, the mechanical energy of the piece is conserved If the inclined plane is not smooth and the block is subject to friction, and a force F is applied to the block in the opposite direction and equal to the friction force, then can the mechanical energy of the block be considered to be conserved?

Conservation
Because the later added force is equivalent to the friction force
In this way, there is no conversion from mechanical energy to internal energy
To tell you the truth, this question is not rigorous enough