Seat (Saddle)

The seat may look like a small, unimportant part of a bike, but it actually does have some importance.  The way it is shaped and positioned does affect the bike.  Different bikes have different shapes of saddles.  For example, racing bikes, triathlon bikes, and mountain bikes all have different positions and shapes of a saddle because they are used for different things.  Don't underestimate the power of the saddle because it can also make your biking experience very comfortable or very uncomfortable.

Gears

Gears are simple machines.  They're the "wheel and axle."  They are used to transfer motion and movement in the bicycle.  Some bikes have very complex gears and some have very simple gears, it just depends on the bike.  But they are very important part of the bike, allowing it to go at different speeds depending on where they are riding the bike.

Pedals

The Pedals on a bike are part of a simple machine: wheels and axles.  They are what move the tires on the bike.  Without them, there would be no motion on the bike.  The rider applies force onto the tires which in turn move the bike.

Brakes

The brakes applied on the bike create friction.  They are very important to help the bike stop.  There is also inertia applied to the bike when the brakes are applied to the bike.  The bike doesn't stop immediately, it takes a few seconds for the bike to completely stop.

Force in Bicycles

The two forces applied to bikes are external and internal forces.

• Internal forces are applied by the rider of the bicycle or the friction.  The rider applies the force through steering the bike.  It happens in the handlebars, wheel, and pedals.  It is generally a torque that is applied.  The friction is caused in many different areas: from the ground, the gears, the brakes, and the pedals.
• External forces are applied from gravity.  The pull of gravity causes the external force of the bike. There is the riding resistance the ground creates, the air-resistance and drag the air creates, and force from braking.

References

http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics

http://en.wikipedia.org/wiki/Bicycle_saddle

http://www.ceeo.tufts.edu/robolabatceeo/K12/classroom/gears.shtml

Physics Summary

So as you can see, there are many different factors that affect physics in bicycles. It was hard to figure out what parts of the physics I wanted to cover.  So just a little review:

• The Handlebars are a very important part of the bicycle making it able to be steered by the rider.  The physics involved are motion and steering angle.
• The gears are a simple machine (wheels and axles) that allow the bike to go at different speeds.  They also have motion involved along with torque and speed.
• The tires make the bike move and help with steering the bicycle.  They also make the bike turn.  Physics in tires include torque, motion, and friction.
• Internal forces and external forces are applied to bicycles through gravity, friction, the rider, brakes, steering, etc.