Physics: Understanding Forces

Force

• Force is a push or pull, present in many actions.
• Four types: applied, normal, gravitational, and friction.

Applied Force

• Applied force is the force you apply to an object (e.g., dribbling a ball, pushing a cart).

Normal Force

• Normal force is a perpendicular force exerted by a surface on an object to prevent it from falling or moving through the surface (e.g., table supporting a book, court making a ball bounce).

Gravitational Force

• Gravitational force pulls objects towards the Earth.
• Essential for maintaining the solar system and atmosphere.
• Keeps objects on the ground.

Friction

• Friction opposes motion between surfaces in contact.
• Four types: static, sliding, rolling, and fluid.

Static Friction

• Prevents an object from moving when force is applied.
• Ex: Pushing a stationary block.

Sliding Friction

• Resists motion during sliding.
• Also known as kinetic friction.
• Ex: A child sliding down a slide.

Rolling Friction

• Resists motion during rolling.
• Ex: A basketball rolling on the court.

Fluid Friction

• Resists motion through a liquid or gas.
• Also known as viscous drag.
• Ex: Swimming.

Newton's Laws of Motion

Newton's First Law (Inertia)

• A body remains at rest or in constant motion unless a force acts upon it.
• Ex: A ball rolling on a field will continue unless kicked.

Newton's Second Law (F=ma)

• Force equals mass times acceleration.
• Formula for calculating net force.
• Unit of force is the Newton (N).

Newton's Third Law (Action-Reaction)

• For every action, there is an equal and opposite reaction.
• Ex: When you dribble a ball, it exerts an equal and opposite force back on your hand.

Energy

• Energy enables work.
• Nine main types: potential, kinetic, mechanical, chemical, thermal, electrical, radiant, sound, and nuclear.

Potential Energy

• Stored energy.
• Ex: Lifting a hammer.

Kinetic Energy

• Energy of motion.
• Ex: A hammer about to hit a nail.

Mechanical Energy

• Sum of potential and kinetic energy.
• Ex: A hammer already hitting a nail.
• Potential = Future Tense (stored energy)
• Kinetic = Present Tense (motion energy)
• Mechanical = Past Tense (work has already been done)

Chemical Energy

• Energy stored in chemical bonds.
• Released during chemical reactions.
• Ex: Combustion (fire).

Thermal Energy

• Associated with heat.
• Temperature rise causes faster molecular movement.
• Three transfer methods: conduction, convection, radiation.

Conduction

• Heat transfer through direct contact.
• Ex: Stirring hot coffee with a metal spoon.

Convection

• Heat transfer through fluid movement (liquid or gas).
• Ex (not given in text): Hot air rising.

Radiation

• Heat transfer through electromagnetic waves.
• Ex (not given in text): Heat from the sun.