Have you ever played on a backyard water slide?
It’s one of our favorite kinds of summertime
fun!
You just lay a piece of plastic on the
lawn, spray some water on it from a hose or
a sprinkler, get a running start, and then…
you can guess what happens next.
You slip and you slide!
It’s so much fun!
But even when it comes to fun, we here at
SciShow Kids love to ask our favorite question…
Why?
So let’s stop to think about why this little
bit of summer fun is possible.
First, let’s think about all of the things
that you need to make a water slide work.
You need a long piece of plastic, and you
need water, and then you need...well...you!
So somehow the plastic, water, and you work
together to create slipperiness.
How do they do that?
Well, for one thing, you can only tell if
something is slippery or not, if you’re
touching it, right?
For example, a wet bar of soap can only slip
out of your hand if you pick it up.
And in the same way, a water slide will only
work if you jump onto it!
So, slipperiness happens when two things touch.
And when two things touch, they rub against
each other.
Sometimes, those things will slide around
against one another, like the wet bar of soap
against your hand, or your body on the water
slide.
But other times, they don’t.
Sometimes, two things that are touching actually
keep each other from sliding.
Can you think of some things that aren’t
slippery?
Well, Squeaks can drive up his ramp without
sliding back down.
And I can sit in my chair without falling
out.
What makes these things not slippery?
It’s called friction!
Friction is a force between two surfaces that
are trying to slide against each other.
The more friction there is, the harder it
is to get those two surfaces to move across
each other.
Take a book and push it across a tabletop.
It’s not hard to move, is it?
What if you took that same book outside and
pushed it on the sidewalk?
Would it move as easily?
Probably not!
That’s because the sidewalk is rougher than
the tabletop.
And that rough surface creates more friction,
when the book moves across it.
So, how much friction there is between two
things, depends on what kinds of surfaces
they have.
Here’s another example: Think about when
you’re just walking around.
Normally, you’re not slipping and sliding
all over the place when you walk down the street.
That’s because there’s lots of friction
between the bottoms of your shoes and the
sidewalk.
That friction keeps you from sliding.
But have you ever stepped on a patch of ice?
It can be really slippery!
That’s because the ice is super smooth,
so it creates less friction than the regular,
dry pavement does.
So … what does all of this tell us?
It tells us that things are more slippery
when there’s less friction.
Let’s see if that helps us understand how
our backyard water slide works.
What do you think would happen if you tried
to go down the slide without any water?
I don’t think you’d be able to slide at
all!
And what do you think would happen if we had
water on the grass, but no plastic?
I don’t think you’d be slipping, either!
The plastic slide gives you a smoother surface
to play on than the grass.
So that helps make it more slippery.
But you wouldn't get very far if you tried
to slide just by throwing yourself on the
plastic.
So the secret here must be the water!
The water makes it so there’s very little
friction!
The water comes between the two surfaces that
are touching, that is, between the plastic
and you, to make a slippery layer that lets
you go shooting down the slide!
Do you want to see some friction in action in other places?
You can do experiments right at home … if
you’re careful!
You’ve probably noticed that you can walk
around on smooth floors, like ones made of
wood or tile, in your sneakers and not slip.
But if you’re only wearing socks, you can
slide across the floor!
Why do you think that is?
And try pushing the book across the table
again, but using different surfaces.
Does it make a difference if you try to push
the book across, say, a bath towel?
What if you tried to slide it across a metal
baking sheet?
Keep experimenting and let us know what you
discover!
And thanks for joining us!
If you have any questions about waterslides or
bikes or flowers or anything at all, just
grab a grown up and let us know in the comments
below.
Or send us an email to kids@thescishow.com!
And we'll see you next time!
