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Wednesday, April 25, 2012

Isaac Newton and the 3rd Law of Motion

Isaac Newton was a great Christian, inventor and scientist. He messed around with light, sound, gravity and motion (and probably more than that). One of his most famous works was "Newton's Laws of Motion" which he tested and proved. The new laws of motion disproved Plato's laws of motion from way back during the time of the ancient Greeks. Plato said that "Things want to stay at rest." Plato was saying that the reason things stop moving is because  their natural instinct, I guess you could say, was to not move, but to stay where they are. Newton said that "Things in motion tend to stay in motion, and things at rest tend to stay at rest." much different from what Plato was saying. Newton's laws were proven with the discovery of two thing, gravity and friction. I will go into more discussion on this at another time, because in this post I'm supposed to be talking about Newtons 3rd law of motion.

Newton's 3rd law of motion states this: "For every action, there is an equal and opposite reaction."
I'm sure that you have heard of this before. Have you ever taken time to stop and think about it though? What was Newton talking about?

A good example of the 3rd law is a bullet. First there is a reaction, then an action, then an other reaction.
The first reaction is when the hammer hits the back of the bullet, igniting the primer which ignites the gun-powder. When the gun powder burns, it expands, in the form of a gas, at a very fast rate. That is the reaction
Then the pressure in the brass chamber forces the lead out of the front of the cartridge, down the gun barrel and on to its target. That is the action.
The second reaction happens when the pressure from the gun powder forces the brass cartridge backwards. This is the reason for the kick when you shoot a gun.















Another good example is a rocket. A rocket engine forces pressure out of the back of the rocket, thus propelling the rocket forward.











Here is another one for you.
Here is a rock that weighs 2,000 lbs. you push on it with a force of 40 lbs. Since the rock weighs more than 40 lbs, it is able to push on you with the same amount of force that you push on it, which cancels out any force and the rock does not move.

    40
-2,000
-1,960 lbs



You still need 1,960 lbs of force to move the rock.














Now say that you are the Incredible Hulk and you push on the rock with a force of 3,000 pounds. since the rock is only 2,000 pounds, it can only exert 2,000 pound on you. So lets do some math.

 3,000
-2,000
 1,000 lbs.

So since the force of you pushing is greater than the weight of the rock, which can also be called the force that the rock is pushing on you, you are able to move the rock.



I hope this has helped you understand Newton's 3rd Law of Motion better. There are so many examples of this law out there, it's not even funny.

Matt

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