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Unit 1: Mechanics Page 19
minutes ago, would you have “proved” that gravity accelerates
gotten it right? It’s conventional all things equally no matter what
wisdom to think that the heavier their weight, but there is no real
object falls faster. evidence that he actually used the
Unfortunately, conventional Leaning Tower of Pisa to do it.
wisdom isn’t always right. Gravity Friction
accelerates all things equally. In
other words, gravity makes all Now let’s talk about the other ever
things speed up or slow down at present force on this Earth, and
the same rate. that’s friction. Friction is the force
between one object rubbing
This is a great example of why the
scientific method (more on this against another object. Friction is
what makes things slow down.
later) is such a cool thing.
Without friction things would just
Many, many years ago, there was keep moving unless they hit
a man of great knowledge and something else. Without friction,
wisdom named Aristotle. Whatever you would not be able to walk.
he said, most people believed to be Your feet would have nothing to
true. The trouble was he didn’t test push against and they would just
everything that he said. One of his slide backward all the time like
statements was that objects with you’re doing the moon walk.
greater weight fall faster than
objects with less weight. Friction is a very complicated
interaction between pressure and
Everyone believed that this was the type of materials that are
true. Hundreds of years later touching one another. However,
Galileo came along and said “Ya when you take a closer look at it,
know...that doesn’t seem to work it's really quite complex. What kind
that way. I’m going to test it” The of surfaces are rubbing together?
story goes that Galileo grabbed a How much of the surfaces are
melon and an orange and went to touching? And what's the deal with
the top of the Leaning Tower of this stick and slip thing anyway?
Pisa. He said, “Look out below!” Friction is a concept that's many
and dropped them! scientists are spending a lot of time
By doing that, he showed that on.
objects fall at the same rate of Static friction is the friction
speed no matter what their size. It between two objects that are not
is true that it was Galileo who moving. Kinetic friction is the
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