Overview
This lecture introduces force, motion, and Newton's First Law of Motion, explaining the relationship between inertia, mass, and changes in movement.
Forces and Their Types
- Force is any push or pull that causes changes in an object's motion.
- Contact force requires touching surfaces; friction is a type of contact force resisting motion.
- Non-contact force acts at a distance, such as gravity between the Sun and planets.
Motion and Its Aspects
- Motion occurs due to unbalanced forces acting on objects.
- Speed is how far an object travels in a set time.
- Velocity is speed with a specified direction.
- Acceleration is how quickly velocity changes.
Newton's First Law of Motion (Law of Inertia)
- An object at rest stays at rest unless acted on by an unbalanced force.
- An object in motion remains in motion at the same velocity unless a force acts on it.
- Inertia is the tendency of an object to resist changes in its state of motion.
Inertia and Mass
- Inertia depends on the mass of the object; more mass means greater inertia.
- Massive objects resist changes in motion more than lighter objects.
Real-life Examples and Demonstrations
- A car stopping abruptly causes you to lurch forward due to inertia.
- Seat belts apply an external force to stop your motion safely in a car.
- In space, a spacecraft moves at constant speed unless acted on by an engine or external force.
- Activity: Flicking a cardboard under a coin demonstrates inertia—the coin remains at rest unless acted on quickly.
Key Terms & Definitions
- Force — A push or pull causing motion changes.
- Contact Force — Force from objects touching each other.
- Friction — Resistance to motion between surfaces in contact.
- Non-contact Force — Force acting at a distance, like gravity.
- Speed — Distance traveled per unit time.
- Velocity — Speed with direction.
- Acceleration — Rate of change of velocity.
- Newton's First Law of Motion — Objects stay at rest or in uniform motion unless acted on by an unbalanced force.
- Inertia — Property of matter resisting changes in motion; depends on mass.
Action Items / Next Steps
- Complete the coin, glass, and cardboard inertia activity.
- Review Newton's First Law examples in daily life.