Pedaling Through the
Have you ever gotten on your bicycle
and wondered how it works? Bikes are really a bunch of
simple machines that work together. Wheels, pedals,
gears, and brakes are all simple machines.
here to learn more about the
simple machines in a bike. If you'd like to know more
about a mountain bike's suspension, click
If you want to understand how bicycles
work, you also need to know a little bit about physics.
Bicycles obey the laws of physics. The laws of physics
that you should know to be able to understand more about
your bike are force and motion, gravity, inertia, and
FORCE AND MOTION
A force makes things move, but a force
can also stop things from moving. When you pedal a bike,
you use your muscles to create a force. You are like the
engine for your bike. You push the pedals in a circle to
start a forward motion.
When you squeeze the hand brakes, you
are also exerting a force which stops the motion of your
bike. Motion is another name for movement. Speeding
motion up is called acceleration. Slowing down motion is
TO THE TOP
Do you remember when you first got on
a bike? You probably fell a lot. The reason you fell is
because you were too young to make the wheels go fast
enough to keep the bike going in a forward motion, so
gravity pulled you down. (In inertia,
you will learn why forward motion is so important.) When
you became older, you learned how to make the wheels go
fast enough, so you could stay up.
When you make the wheels go fast
enough, the wheels create a force that acts as an
anti-gravity force. A bike works like a gyroscope. A
gyroscope is a cool thing that defies gravity. By putting
a string around the axle and pulling hard, you make it
spin very fast. So basically, when you are riding your
bike, you're defying gravity!
Here are pictures of a gyroscope
still and spinning. Cool!
TO THE TOP
Friction slows things down. Friction
also tries to stop one surface from sliding on another.
If you were trying to ride your bike on an icy road,
there would not be enough friction between the surface of
the tires and the surface of the ice. You would slide and
not have control of your bike.
Another way friction has to do with
bikes is in the parts of a bike. For example, if you want
less friction on your bike, put oil on the chain and
gears, so you don't have so much friction to slow you
down. The oil helps your gears turn easier, and that
helps keep gears from wearing out.
You can feel friction when you rub
your hands together and they get warm. Now put soap on
your hands and rub them together. Do your hands move
easier with soap? That's like putting oil on
TO THE TOP
According to Newton's First Law,
inertia is the tendency for an object that is moving to
keep moving and the tendency for an object that is at
rest to stay at rest.
To prove that inertia exists, go
outside and pedal your bike fast and then brake. Did you
stop immediately? Or did you skid a little bit? Because
of inertia, you should have skid a few inches.