Laws of Motion


First Law - Inertia

With no outside forces, objects stay in one place or continue moving at the sape speed and sirection.The first law says that an object at rest tends to stay at rest, and an object in motion tends to stay in motion, with the same direction and speed. Motion (or lack of motion) cannot change without a force acting on it. In other words, if nothing is happening to an object (the chair in the living room), and nobody moves it, it will never ​go anywhere. If you are riding your bike in a specific direction, unless something changes (friction, turning the handle bars), you will always go in that direction. Forever. 

Second Law - Acceleration

As acceleration increases, the force increases.The second law says that the acceleration  of an object produced by a net (total) applied force is directly related to the magnitude of the force, the same direction as the force, and inversely related to the mass of the object (inverse is a value that is one over another number... the inverse of 2 is 1/2). The second law shows that if you exert the same force on two objects of different mass, you will get different accelerations (changes in motion). The effect (acceleration) on the smaller mass will be greater (more noticeable). The effect of a 10 newton force on a baseball would be much greater than that same force acting on a truck. The difference in effect (acceleration) is entirely due to the difference in their masses. 

Third Law - Opposed Force​
The third law says that for every action (force) there is an equal and opposite reaction (force). Forces are found in pairs. The third law says that for every action (force) there is an equal and opposite reaction (force).

Think about the next time you sit in a chair. Your body exerts a force downward and that chair needs to exert an equal force upward or the chair will collapse. It's an issue of symmetry. Acting forces encounter other forces in the opposite direction. There's also the example of shooting a cannonball. When the cannonball is fired through the air (by the explosion), the cannon is pushed backward. The force pushing the ball out was equal to the force pushing the cannon back, but the effect on the cannon is less noticeable because it has a much larger mass. That example is similar to the kick when a gun fires a bullet forward. ​

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