西雅圖‧高雄 大城市‧小角落 我的心世界

Rowboat (aka Dragon Boat)

The conditions for this scenario are also idealized. There are no waves creating extra motion and the boat is moving at constant velocity, so there is no acceleration.

Free Body Diagram

The gravitational and buoyant forces directly oppose each other in magnitude and direction because the boat is not accelerating in either of those directions. There is a F_push in this scenario that is applied by the rowers, causing the boat to move in that direction. There is also the F_drag applied to the boat. Since air resistance is still negligible compared to the water resistance, air resistance was left out of the diagram. The F_drag and the F_push are opposite because the F_drag opposes the direction of motion. They are also equal in magnitude because the boat is not accelerating. Since the boat is not accelerating, the net force is zero. The diagram demonstrates this because all of the force vectors cancel out.

Energy Cubes

All of the energy in the video above starts as chemical energy in the person. As the person uses that energy, they will generate heat. This thermal energy is transferred from the person’s chemical energy and goes into the surrounding air as thermal energy. Some energy is also lost as thermal because of the drag force, so this energy is shown as going into the water. All of the rest of the energy is transferred into kinetic energy, moving the boat forward.

Some more thoughts... (  please click me!)