Did you know that you transfer about ninety percent of your force upon a pedal of a bike into kinetic energy? Riding a bike is so simple but there is so much physics behind it. As you ride a bike there are multiple forces on you. There is a force of gravity downwards on you, so as you slow down, the force of gravity will push you and the bike down. There is also a drag force and frictional force acting on you and the bike. The drag force is the air resistance you feel when you go downhill. If you're going at a high speed with your bike then you can feel the air resisting you from going down the hill. Also you can't forget the frictional force between the tires and the road. Then there is a force pushing you forward which is caused by the work the person does by pedaling. As the person decreases its work then, the frictional force will be greater causing the bike to slow down. But if the person increases its work, the force going forward will be greater than the frictional force causing the bike to speed up.