It is helpful when describing forces acting on an object to label their direction. Since forces have both Magnitude (Size) and direction, they are said to be vector quantities. Vectors are represented by arrows and can be added if they face in the same direction or subtracted if they are in the opposite directions. Vector diagrams are pictures which include vector arrows to represent all of the forces which act on a single object.
Draw a vector diagram of a bicycle being pedaled and label all of the forces which act on it. If you are unsure about all of the forces that act, search google to help you figure out which forces act and then label them with arrows in your diagram.
Bicycle with thick tires, like mountain bikes, tend to go slower than bicycles with thin tires, like road bikes, when you apply the same amount of force, even if the bicycles are the same weight. This is due to the frictional force between the road and the tire.
According the the conservation of energy theory, energy cannot be created or destroyed. However, since the bicycle with smaller tires is traveling faster than the bicycle with the larger tires, it has more kinetic energy (the energy of movement). Where does this excess energy go?