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**A Pelican Landing on Water**
Many waterfowl, like this pelican, frequently use water as a preferred landing surface rather than using land. Though it looks like the pelican simply begins to float on the water as it lands, there are actually numerous phenomenon occurring that allow the pelican to land safely on the water. The most important among these are Friction, Gravity, and Newton's Third Law of Motion. Here is a look at how each is essential in the landing of a pelican on water:


 * __ Friction __** : Whether it be a bird, plane, or automobile, friction is the phenomenon that all moving objects use as a means of deceleration. Friction is the reaction a moving object has when it comes into contact with other matter: it slows down. Look closely at the pelican above: its wings are spread wide open, creating the most surface area for air to flow over, creating the most friction. This allows the bird to slow as it nears the water. Also, observe the water itself. When the bird hits the water, a dense liquid flows over its feet and lower body, creating a large amount of friction, rapidly slowing the bird, which allows it to gain a position that enables it to float on the surface of the water.


 * __ Gravity __** : Gravity is the force that attracts all physical bodies toward one another. On Earth, gravity is what acts on us and pulls us toward the ground. Gravity's constant pull is easily seen in the picture above: the pelican is falling, but is not using its wings, its main means of movement, to do so. A pelican uses gravity as a means of propulsion while landing, to leave its wings free to slow the pelican's velocity to a point at which it is safe to land. Gravity provides a safe, reliable force for the pelican, enabling it to land.


 * __ Newton's Third Law of Motion __** : Newton's Third Law simply states: "Every action will have and equal, and opposite, reaction". This means that for every force that is applied on an object, and equal and opposite force pushes back. In many cases, this will create a state of equilibrium. In the picture, the bird impacts the water, and the water pushes back with equal force. This causes the bird to stop moving and reach a state of equilibrium with the water, allowing it to float. The waters liquid state accounts for the splash: the water molecules cannot keep a hold on one another and are moved by the force of the bird hitting the water. However, they still apply an equal and opposite force.

Physics Concepts: Friction, Gravity, Newton's Laws Sources: Layton, Julia. "How Does Gravity Work?." 2011. Print. . "Friction." //Physics4Kids//. N.p., 13/12/2011. Web. 14 Dec 2011. . "(18a) Newton's Third Law." //NASA.gov//. NASA, n.d. Web. 14 Dec 2011. .