Question

concepts
section 6.1

1. newtons first law states that no force is required to maintain motion in a straight line at constant speed. if newtons first law is true, why must you continue to pedal a bicycle on a level surface to keep moving?

Explanation:

Newton's first law applies to an ideal situation with no external forces. In reality, when pedaling a bicycle on a level surface, there are external forces like air resistance and friction between the bicycle's components (e.g., chain, gears) and between the tires and the road. These forces act in the opposite direction to the bicycle's motion. To keep the bicycle moving at a constant speed (or accelerating), you need to apply a force by pedaling. This applied force counteracts the resistive forces (air resistance and friction). If you stop pedaling, the net force on the bicycle becomes the sum of the resistive forces (since there is no applied force from pedaling anymore), and according to Newton's second law \(F = ma\) (where \(F\) is the net force, \(m\) is the mass of the bicycle - rider system, and \(a\) is the acceleration), the bicycle will decelerate (\(a<0\)) and eventually stop.

Answer:

You must continue pedaling to counteract air - resistance and friction forces.