Overview
This lecture explains why it is harder to start moving a bicycle than to keep it moving, using Newton's three laws of motion.
Newton's First Law: Law of Inertia
- Objects at rest remain at rest, and objects in motion remain in motion unless acted on by an outside force.
- The tendency of objects to resist changes in their state of motion is called inertia.
- Overcoming inertia is needed to start moving a stopped object, such as a bicycle.
Newton's Second Law: Force and Acceleration
- Newton's Second Law states that force equals mass times acceleration (F = m × a).
- To accelerate an object, a force must be applied.
- Greater mass requires more force for the same acceleration.
- Pedaling a heavier bicycle demands more effort due to increased mass.
Newton's Third Law: Action and Reaction
- For every action, there is an equal and opposite reaction.
- When a bicycle tire pushes backward on the ground, the ground pushes forward, moving the bicycle ahead.
- Each bicycle tire creates an action/reaction force pair with the ground.
- The Earth's large mass means it doesn't noticeably move from the bicycle's force.
Key Terms & Definitions
- Inertia — The resistance of an object to changes in its motion or rest.
- Force — A push or pull acting upon an object, measured as mass times acceleration.
- Action/Reaction Pair — Two forces described by Newton’s Third Law, equal in strength but opposite in direction.
Action Items / Next Steps
- Review Newton’s three laws of motion and relate them to real-life examples, such as riding a bicycle.