Newton’s third law states that “For every reaction there is an equal and opposite reaction”. This led us to ride the bicycle as we exert a downward force on bicycle and the bicycle exerts an upward force on us.
Now, the question arises that what happens to our bicycle when we stop pedaling.
Answer to your question is FRICTION.
Friction is an opposite force which resists the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.
When surfaces in contact move relative to each other, the friction between the two surfaces converts kinetic energy into thermal energy (that is, it converts work to heat). Similarly, in our case when bicycle move in contact with the road, the friction between surfaces starts converting kinetic energy into thermal energy so when we stop pedaling there remains no force to overtake the friction so then the kinetic energy slows down the bicycle as it continuously subtracts the moving force and so after sometimes the bicycle begins to rest.
Friction may lead to wear and tear which may leads to performance degradation. It also produces unnecessary heat. For example- car engine becomes hot due to friction. Besides of this, friction is desirable and important in supplying traction to facilitate motion on land. Most land vehicles rely on friction for acceleration, deceleration and, changing directions.