Newton's Three Laws of Motion
by Matthew Petty
Newton's 1st Law of Motion
An object at rest will stay at rest while an object in motion will stay in motion.
This means that an object will stand still unless a force, such as you pushing it or the wind blowing on it, knocks it over. A moving object will stay in motion, unless a force such as friction stops it.
When the marble goes down the ramp, a force works with it. When it goes up, the force works against it. When it is still, force neither goes with or against it, so it will not go up or down.
Newton's 2nd Law of Motion
Applied force will change velocity of an object if it is pushed or pulled. This change in velocity is in proportion to the amount of force.
This means that an object will react to different thing. If you push it slowly, it is going to go forward slowly. If you pull it back quickly, it will move quickly backwards.
The dog is pulling forward, so the sled is moving forward.
Newton's 3rd Law of Motion
For each action, there is an equal but opposite reaction.
This means that, for example,if you have a computer sitting on a table, the table will push the computer up, wich keeps it from falling.
Picture is pretty self explanatory. Air rushed downward while the balloon is forced upward.
Sources:
Yahoo answers
wikipedia
zonalandeducation.com