It sounds like you're asking about the forces that act on water as it flows through a pipe or channel. There are a few pairs of opposing forces that are relevant here:

1. Pressure and Friction:

* Pressure: The force exerted by the water itself due to its weight and confinement. This pressure pushes the water forward, driving its flow.

* Friction: The resistance the water encounters as it moves along the pipe or channel walls, as well as the internal friction within the water itself (viscosity). This opposes the flow.

2. Gravity and Resistance:

* Gravity: If the pipe or channel is inclined, gravity will pull the water downwards, contributing to its flow.

* Resistance: This can include friction, but also other factors like the shape of the pipe or channel, obstructions within the flow, and the water's own inertia.

3. Inertia and Resistance:

* Inertia: Water's tendency to resist changes in motion. This means that it takes force to get water moving and to stop it once it is moving.

* Resistance: This encompasses all the forces that oppose the water's motion, including friction, gravity, and the shape of the pipe or channel.

Important Note: The specific forces acting on water in a particular situation will depend on the specific circumstances, such as the pipe's diameter, the water's velocity, and the presence of bends or other obstacles.