Did you know?-Humans are made up of 95 percent water. This means that only 5 percent of a person’s mass will sink in a large body of water due to the force of gravity. This allows the body to float near the surface of the water, but not on top of it.

-To stay up, one must push themselves up with their hands or feet to counter the gravitational force. This is also called Swimming

Some physics behind swimming!

• To move forward, a force must be applied to help the body accelerate from rest in a certain direction.

• This is more than possible with knowledge of Isaac Newton’s third law.

Isaac Newton’s third law

• For every action, there is an equal and opposite reaction.

• Hence, you have to push back on the water as hard as you can and it pushes you forward with an equal force.

However…

• There is drag. Drag is a force that opposes motion and will reduce a person’s velocity while swimming

• To reduce drag, you can try shaving your hairy legs, wearing streamline swimming attire, and swimming in a streamline shape.

• These precious seconds cannot be spared when racing against opponents to gain possession of the ball during a water polo match!

• The drag can be divided into two components: pressure drag and skin friction drag.

• Pressure drag comes from the frontal area exposed to the water and the separation that occurs behind the swimmer.

• However, the flow around a swimmer is already turbulent. Therefore, a swimmer must streamline his body to reduce the amount of separation.

• The drag from the skin friction, on the other hand, increases when the swimmer becomes more streamlined since more surface area is exposed to the water. This is not really a concern, as the pressure drag is dominant and, therefore, the overall drag decreases.

Swimmer producing a lot of drag Streamlined Swimmer

Thrust

• Arm stroke produces the majority of the thrust. • The difference between swimmers is how the arm

stroke is used to produce thrust. The best swimmers not only achieve thrust by pushing back on the water, but also by moving their hands and arms like a propeller.

• The most obvious production of thrust does come from pushing back on the water like a paddle wheel or rowing a boat. In fact, the straight arm pull was originally thought to be most efficient.

• This stroke involves moving the arm along a curvilinear path. This way the swimmer is always pushing back on still water. The advantage is that the still water offers more resistance than the water that is already moving back.

Lift

• Even though the swimmer is moving from right to left, his hand is moving from top to bottom and the lift force contributes to the thrust.

• It should also be noted that the hand must continue to move in the directions perpendicular to the direction of forward movement in order for this lift force to be produced.

The kick• The kick provides a stabilizing effect in addition to the propulsive

force.• Most swimmers only get a small amount of propulsive force from

their kick. • The first way to improve the kick is to keep the feet in the water.

When a swimmers feet enter the water, a significant amount of air enters as well. The air increases the drag as well as reducing the propulsive effect.

• The best swimmers go further by moving their feet during the kick to produce the same lift force achieved by their hands.

• Due to the asymmetrical armstroke of the freestyle and backstroke, the kick also acts as a stabilizer.

• In these two strokes, as one arm is recovering out of the water, the other is producing a propulsive force.

• Since this force acts to the side of the swimmers center of gravity, a moment is applied to the body which causes the swimmer to twist in the water.

• This twist increases the pressure drag as the body becomes less streamlined. A proper kick helps to keep the body streamlined, thereby reducing the drag.

Conclusion

• As one can see, the gap between champion swimmers and weak swimmers is the ability to use the basic principles of fluid dynamics to ones advantage.

• Want to do well in water polo? Then you would have to train up on your swimming speed and stamina!

• http://fitnesssutra.com/fs-content/blogs/79/uploads/images/swimming.jpg

• http://www.chsglobe.com/sports/2009/10/physics-of-swimming/

• http://wings.avkids.com/Book/Sports/instructor/swimming-01.html