Physics of Bicycles

Physics plays a vital role in all that we do, whether we are aware of it or not. The sport of bicycling is no exception to the physical laws of Mother Nature.

Friction is a resistive force that always acts in a direction that is opposite to the motion of a body. Frictional forces are dependent on two components; the coefficient of friction and the normal force.

Friction = (µ)(n)

There are two different types of frictional coefficients, static and kinetic. The coefficient of static friction is the frictional force that must be overcome before any motion commences. It is caused by the minuscule contact points between our tires and the riding surface (There is frictional losses present in every mechanical connection on the bike but these will not be addressed within the scope of this article).

The coefficient of kinetic friction is the acting frictional force when our bicycles are in motion. As with all frictional forces, kinetic friction acts in a direction that opposes motion.

The normal force is simply the force that is exerted upon the rider and the bike by the ground. It is in turn equal and opposite to the force that the rider and the bike apply on ground. This is in accordance with Newton’s third law.

Three major frictional forces affect a bicycle, the friction between the tires and the riding surface, friction caused by braking, and the wind resistance. There are other frictional forces acting on the bike such as those found in the bearings and other moving parts, however for the purpose of this assignment only the previously mentioned forces will be discussed.

Frictional forces can also be found between the tires and the surface of the ground. The presence of friction between our tires and the...

... middle of paper ...

...t rest. The second case occurs when the bike suddenly stops but due to their inertia the rider continues to stay in motion.

Gravity is the force of attraction between objects and the center of the earth. It is always present and performing work either for or against you. Gravity is the reason it is harder to bike up a hill than to go down one. When traveling up a hill gravity is working against you. It is a force that pulls you and your bike toward the center of the earth, opposite to your preferred direction. As you continue to travel farther up the hill the force of gravity gets stronger. Because Force = Mass x Gravity (Newton’s second law), a greater force must be applied to the pedals to compensate for the opposing force of gravity.

On the way back down the hill gravity is still doing work on you and your bike only now it is to your advantage.