"Lex II: Mutationem motus proportionalem esse
vi motrici impressae, et fieri secundum lineam rectam qua vis
illa imprimitur." - Newton's Second Law from the original 1687
edition of the Principia Mathematica
Power and Speed
We know from Newton’s second law that the net force
on an object is the sum of all the forces acting on the
object which is proportional to the mass and acceleration.
With bikes, the propulsive force is the force that propels
the rider forward. This force has to overcome four different
resisting forces in order to move from rest according to
David Wilson (Fa - air resistance, Fs - slope resistance, Fr
- rolling resistance, and Fb - average bump resistance).
The equation for the
system is as follows:
Fp – (Fa + Fs + Fr + Fb) = Facc = ma
A bike rider can
adjust his or her gearing to choose any desired leverage or
force ratio but the amount of propulsive force that the
system experiences doesn’t directly mean that the rider is
traveling at a high speed. The resisting forces can greatly
affect the net force of the system and therefore will affect
the net acceleration. David Gordon Wilson continued that “in
riding on smooth, level pavement in still air, at or below
jogging speeds (3 m/s), the main resistance acting on a
bicycle is the rolling friction of the tires.” He continues
to say that “as the cycle’s forward speed is increased,
aerodynamic drag grows quickly and becomes far more
important as a source of resistance.” We can see that the
amount of resisting forces depends on the conditions that
they are in and the speeds that they are traveling at. A
rider who is traveling up a large incline on a very rough
surface with a headwind will have a significantly larger
amount of resisting forces than the prior situation.
The creation of the bicycle that we know today has
three different steps in its history. The first and most
important discovery in the development of the bicycle is
accredited to Baron Karl von Drais because of his “running
machine” which had two wheels and front wheel steering. His
creation, the Draisienne, was improved on by many others
into a pedal equipped bicycle, also known as a velocipede,
which is the second milestone in the creation of the
bicycle. More improvements to bicycles were made like rubber
being added to the rims to improve comfort and tension
spoking which allowed the front wheels to be made larger.
Because the pedals were fixed to the front axle and gearing
that we’re accustomed to wasn’t around, speed was limited to
the amount of distance per pedal revolution. By creating a
larger wheel, one could travel more distance per revolution
and thus travel at a larger speed. These funny looking
bicycles, commonly known as high rollers, were superseded by
safety bicycles. These bicycles had a steerable front wheel,
equally sized wheels, chain drive to the rear wheel, and a
seating position in between the
A Brief Bicycle History
The creation of the bicycle that we know today has
three different steps in its history. The first and most
important discovery in the development of the bicycle is
accredited to Baron Karl von Drais because of his “running
machine” which had two wheels and front wheel steering. His
creation, the Draisienne, was improved on by many others
into a pedal equipped bicycle, also known as a velocipede,
which is the second milestone in the creation of the
bicycle. More improvements to bicycles were made like rubber
being added to the rims to improve comfort and tension
spoking which allowed the front wheels to be made larger.
Because the pedals were fixed to the front axle and gearing
that we’re accustomed to wasn’t around, speed was limited to
the amount of distance per pedal revolution. By creating a
larger wheel, one could travel more distance per revolution
and thus travel at a larger speed. These funny looking
bicycles, commonly known as high rollers, were superseded by
safety bicycles. These bicycles had a steerable front wheel,
equally sized wheels, chain drive to the rear wheel, and a
seating position in between the two wheels. Bicycle
improvements continued to be made, but the creation of
safety bicycles mark the last main milestone.
two wheels. Bicycle improvements continued to be made, but the
creation of safety bicycles mark the last main milestone.
