One of my favorite places to hang out with my friends is the amusement park.
amusement park
My science teacher told us that it's physics that creates the fun, especially on rides that go around in a circle.
With rides that move in a circle and go around steep curves, it's "centrifugal" force that makes you feel like you're being pushed outward.
I think that's why people stay in their seats when a 
roller coaster goes upside-down. 

Let's test out this force!

what you need
a ballpoint pen or pencil
a paper cup (7- or 8-ounce cups work best)
what to do
First, make your own min-bucket. With the pen, poke a hole near the rim of the cup. Then poke one directly across from it on the other side of the cup.

Cut 2 pieces of string about 2 feet (60 cm) long each. Attach each string to a side of the cup by looping it through the hole and tying a knot. 

Now fill your "bucket" halfway with water. Take the ends of the strings in your hand and whip the bucket around in a circle over your head. Be sure to stand away from your friends and any breakable objects. 
(You may want to sway the bucket back and forth a bit before you make a full circle.)
Try to repeat the experiment, but this time fill the cup 3/4 of the way with water. (You can also try to do it with a penny in the cup instead of water.)
When you whipped the cup around, did any water fall out? 
How is this like a roller coaster going upside down? 
Tell us what you think!
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more facts
keisha talk Sir Isaac Newton, a scientist who lived 300 years ago, made observations that explain the behavior of moving objects - like kids on roller coasters. 

One of the important things he noticed is that "a body in motion will move in a straight line unless acted upon by an outside force."

When a roller coaster launches into a loop, you might wonder why you don't fall out. Actually, what you should wonder is why you don't go shooting into the sky! Your body tries to "remain in motion" - in a straight line toward the sky! 

Luckily, you're acted on "by an outside force" - coming from the seat and the floor of the car. They stop you so that you don't go flying!

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