JOAN CARTAN-HANSEN: So a force is a change in motion.
Gravity pulls you down. The ground pushes you up. When forces are in balance nothing happens and you don’t notice it. It’s when they get out of balance that things happen. Ready?
Gravity is the force of attraction between things. It’s what makes things fall.
There are 3 laws of motion discovered by Sir Isaac Newton.
An object that isn’t being pushed or pulled by a force either stays still or keeps moving in a straight line at a constant speed.
(children screaming)
CHILD: Wait a minute. Gravity pulled me down in a straight line. Why did we stop?
JOAN: Well, Newton
If gravity was the only force we’d just keep sliding. Another force called friction slows you down until you stop.
Forces make things move. The bigger the force, or the lighter the object, the greater the motion.
Say you push a toy along the street. It’s pretty easy because the toy is light and you can push or pull with a lot of force. The more force, the faster it moves or accelerates.
CHILD: Right in. Good aim.
JOAN: Say you try to push or pull something really big. It would take a lot of force to get it to move.
Every action has an equal, and opposite reaction.
Forces act in pairs. When the space shuttle lifts off the burning gas pushes out the engine and lifts the shuttle.
When you hit your friend with a bumper car the force pushes him away but the force of his car pushes you back the same amount of force. Hit him softly you both move just a little. Hit him hard, Woo-hoo! Equal and opposite reaction.
The laws of motion are the basis of the science of physics.
It will apply to all the particles in the universe from the smallest atom to even the biggest planets, even this roller coaster.
CHILD: Stay at rest until acted on by an outside force. That’s Newton
CHILD: And when an engine pulls the cars up the hill, that’s Newton
CHILD: And how does the third law apply?
JOAN: And for every action there’s an equal and opposite reaction. First we go up, then we go d-o-o-o-w-w-w-n!
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