General Knowledge - Physics - Discussion

As the fan is attached to a simple boat it will move in opp. Direction due to newton's 3rd law.

But given boat is a sailboat.

As fan exert a force on the sail (the huge cloth attached to the boat to enable the boat move with wind energy) boat will not move because sail and fan are attached to the same boat.

It like a man sit in a trolly exert a force on the trolly. As a result net force is zero and trolly remains stationary.

Fan attached with helicopter lifts the helicopter upward the same way boat will move.

The boat should move in the flow of air.

Dear all,

The boat will not move. Suppose the fan pushes an air molecule and in turn get pushed in opposite direction. Now, this molecule hits the sail of the boat and imparts the same momentum to the sail and hence boat.

In total two forces act on boat forward and backwards----hence zero motion.

This is similar to a person sitting on a boat and pushing it from inside--the boat won't move-----man pushes the boat in +x direction and boat pushes the man in -x direction as the man is on boat it means the boat is being pushed in -x direction----hence boat is pushed in +x and -x direction. No resultant motion.

This is in tune with newton second law --which states that only external force can change the momentum of a body and not internal forces. F (ext) =dP/dt.

Question is not clear.

Because whether the fan has been fitted inside compartment for air circulation or it has been fitted on the edge of boat? in two cases, it will have differnt answer, for first, it will nor move, for second, it will move.

I think the boat moves in the same direction in which the air blows. This is due to the sail pulling the boat in the same direction as the air. Had it been a fan (assumed to have a high thrust capability) fitted on a boat without a sail, the boat would've moved in the opposite direction just like a jet engine moves an aircraft.

It moves in the same direction in which the air is blown.

It will move in opposite direction. But the thrust produced by the fan should be greater than the weight of the boat.

Question is not appropriate!

If the fan is attached to a boat and directed toward its flaps. Then it will not move.

Answer is the boat will not move.

As the air is blown on fan so to move forward fan give equal and opposite reaction to boat Ian the opposite direction s boat will be at the same place.