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Forces of Nature
Forces are the biggest idea in physics. The whole purpose of physics is to study the forces that are found in the universe. The forces could be big, such as the pull of a star on a planet. The forces could also be very small, such as the pull of a nucleus on an electron. Some force affects everything in the universe at all times.
Forces as Energy
Physicists define forces as specific amounts of energy applied to an object. Anything could be a force. If you were a ball sitting on a field and someone kicked you, a force would have acted on you. After receiving the force, you would go bouncing down the field. There are always many forces at work. Physicists might not study them all at the same time, but even if you were standing still, you would have many forces acting on you. Those forces would include gravity, air pressure, wind speed, the strength of your skeleton, the strength of your muscles, and many other smaller forces.
Let's look at the forces acting on that ball. As you sat there, the force of gravity was keeping you on the ground. On a molecular level, the surface of the ball was holding itself together as the gas inside of the ball tried to escape. There may have also been small forces trying to push you as the wind blew. Those forces were too small to get you rolling, but they were there. And you never know what was under the ball. Maybe an insect was stuck under the ball trying to push it up. That's another force to consider.
If there is more than one force acting on an object, the forces can be added up (or subtracted). After coming up with a value, scientists use the value of a Newton to measure the amount of force. The force applied to the soccer ball (from the kick) could be equal to 12 Newtons.
A Formula of Force
There is one totally important formula when it comes to forces, F = ma. That's all there is, but everything revolves around that formula. "F" is the value of the force, "m" is the object's mass, and "a" is the acelleration that happens. As a sentence. "The force applied to the object equals the mass of the object multiplied by the amount of its acceleration." The forces acting on the soccer ball are equal to the mass of the soccer ball multiplied by its change in speed (acceleration). Do you remember the wind blowing on the soccer ball? The forces acting on the ball were very small because the mass of air was very small. Small masses mean small forces unless there is a large accelleration.
Forces and Vectors
We cover the details of vectors on another page. A vector can be used to represent any force. Vectors describe a specific amount of force that is applied in a specific direction. Just kick the ball in an amount and in a certain direction.
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