Final answer:
When you do 200 J of work pulling the oars of a rowboat, the oars also do 200 J of work to move the boat, according to Newton's third law. The actual force that propels the boat is caused by the oars pushing against the water.
Step-by-step explanation:
If you do 200 J of work pulling the oars of a rowboat, the same amount of work is done by the oars to move the boat in the absence of other opposing forces, like drag or friction. This can be attributed to Newton's third law, which states that for every action there is an equal and opposite reaction. However, the actual motion of the boat also depends on other factors such as the direction and magnitude of resultant forces.
The force that moves a boat forward when someone rows it is primarily caused by the interaction between the oars and the water the boat is traveling in. When the oars push the water backward, the reaction force of the water on the oars propels the boat forward. This force is generated through the exertion of the rower's arms.