How can you row a boat with a paddle?

[scilearner]

Hello everyone,

 

When you go on a boat and use the paddle and displace water molecules you create low water pressure right? Then why does the boat move forward? I know water would flow from high to low but how can you specfically know that water would fly from high to low in forward direction, can't it happen in any direction? Also why does paddling one side make the boat turn? Thanks!

[DJBruce]

Rowing a boat is all about Newton's Third Law. You apply a force propelling the water backwards, and the water provides and equal and opposite force propelling you forward. As far as I know it has nothing to do with pressure.

[insane_alien]

pressure is how the force is transmitted to the water. force over the area of the paddle.

[scilearner]

Right!! Thanks for all the answers. I understand newton's third law at work here but if you displace air molecules don't other air molecules come to fill the space. Doesn't the same thing happen with water. I think I'm talking about buoyancy force. Also I still don't understand why paddling one side make it turn?

[swansont]

Also I still don't understand why paddling one side make it turn?

 

The force is not at the center-of-mass, resulting in a torque.