We’ve been out looking for rocks to add
to our rock collection!
And as you can see, Squeaks and I have found
a ton of awesome rocks!
We’ve just put them in a box and are ready
to take them back to the fort, so we can learn
more about them.
But … it looks like we might have collected
a few too many!
This box is really heavy...too heavy to carry!
So, I wonder if we can pull the box back to
the Fort.
Squeaks, do you want to give it a try?
Rats!
Oh...sorry, Squeaks!
I mean, oh man!
That was a good try, but we’re going to
have to think of something else.
If you've spent some time with us recently,
you probably know that we can use simple machines
to help us do work.
In the past we’ve used levers … ramps...
...and pulleys … to help us move big, heavy
things.
But neither of those is quite the right machine
for this problem.
However, there’s another simple machine
that I think will do the trick.
This simple machine is called a wheel and
axle.
You already know what a wheel is!
And an axle is the bar that goes into the
middle of a wheel.
In order for a wheel to work, it has to spin.
And a wheel spins on an axle.
I bet you can think of lots of things that
use wheels and axles.
Like, cars and trucks, bicycles, rollerskates,
rollerblades... and ...our wagon!
Of course!
We can put the box in our wagon and pull it
back to the fort.
Great idea as usual, thanks Squeaks!
Our wagon has two axles...and two wheels on
each axle.
So we’ll just put the box inside the wagon.
Okay Squeaks, pull on the handle!
..and the box is on the move!
We solved the problem!
But how do the wagon’s wheels and axles
help us to do work?
It all comes down to how much force we need
to move the box.
We’ve talked about forces before: They’re
the pushes and pulls that things put on each
other.
In this case, the force we’re concerned
with is the one we use to pull on the box.
When the box was on the ground, Squeaks tried
to put a big force on the box to pull it.
But even though he pulled really hard, he
could only move it a little bit.
But when the box was in the wagon, Squeaks
was able to pull it all by himself easily!
So it took less force to move the box!
And that’s what this simple machine does.
A wheel and axle changes how much force we
need to move something.
Instead of a big push or pull...we can use
a much smaller one.
And smaller pushes and pulls mean less work
for us.
Because it takes less force to move heavy
things, wheels and axles make it easier to
move something a long way.
That's why they're part of so many things
that help us stay on the go.
And that’s why you’ll see wheels and axles
on buses, scooters, wheelchairs...and even
robot rats!
But Squeaks is one robot rat that’s earned
a break!
Hop in, Squeaks—I’ll give you a ride back
to the Fort!
Thanks for joining us!
If you have questions about machines or forces
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!
See you next time!
