Wuxi medical equipment fan enterprise

As can be seen from the figure, when the fan works, the electric fan blows forward. Because the forces are mutual, the air will give the fan a backward reaction, so the car will move backwards.

For example, when swimming, people paddle backwards and are pushed forward by the water, so people move forward.

Therefore, the answer is: the role of force is mutual;

When swimming, people paddle backwards and are pushed forward by the water, so people move forward.