Kinetic and Potential Energy

• Energy is the ability to do work, measured in Joules (J).
• One Joule is the heat needed to raise the temperature of 0.239 g of water by 1 degree Celsius, or the energy to lift a medium apple one meter.
• The law of conservation of energy states that the total energy of a system remains constant; it can be transformed or transferred.
• Energy cannot be created or destroyed.

Forms of Energy

• Energy exists in two primary forms: kinetic and potential.

Kinetic Energy

• Kinetic energy is the energy of motion; any moving object possesses kinetic energy.
• The faster an object moves and the more mass it has, the more kinetic energy it possesses.
• Examples include a moving car, a flowing river, and a person running.

Potential Energy

• Potential energy is energy stored within an object due to its position, arrangement, or state.
• When the object's position, arrangement, or state changes, the stored energy is released.
• Examples include a rock on a cliff, a stretched elastic band, dynamite, and food.

Types of Energy

• Thermal energy is created by the vibration of atoms and molecules; faster movement equates to more energy and higher temperatures.
• Chemical energy is stored in the bonds of atoms and molecules, holding them together.
• Chemical energy is found in food, biomass, petroleum, and natural gas
• Nuclear energy is stored in the nucleus of atoms and is released during fusion (combining nuclei) or fission (splitting nuclei).
• Electrical energy is the movement of electrons, with electrons moving through a wire known as electricity.
• Radiant energy (light or electromagnetic energy) is kinetic energy that travels in waves (e.g., sunlight, x-rays, radio waves).
• Light is electromagnetic radiation consisting of photons produced when an object's atoms heat up.
• Light travels in waves and is the only form of energy visible to the human eye.
• Motion energy (mechanical energy) is the energy stored in moving objects; faster movement equates to more stored energy.
• Sound energy is the movement of energy through substances in waves, produced by vibrations.
• Elastic energy is potential energy stored in elastic objects when stretched or squashed (e.g., springs, elastic bands).
• Gravitational energy is potential energy associated with the height of an object relative to a lower position.

Energy Sources

• Energy sources can be renewable or non-renewable.

Renewable Energy

• Renewable energy sources are naturally replenished and can be used indefinitely.
• Examples include solar, wind, hydro, geothermal, and biomass energy.
• Renewable energy promotes sustainability, has a lower environmental impact by reducing greenhouse gas emissions, and increases energy security by diversifying sources.
• Solar energy harnesses energy from the sun using solar panels for electricity or thermal collection.
• Wind energy uses wind turbines to convert kinetic energy into electricity.
• Hydropower generates electricity from the movement of water (dams, tidal energy).
• Geothermal energy utilizes heat from the Earth's core for heating, cooling, and electricity generation.
• Biomass energy uses organic matter for fuel, heat, or electricity.
• Marine energy harnesses power from ocean resources like waves, tides, currents, and temperature differences.

Non-Renewable Energy

• Non-renewable energy sources are finite resources that cannot be replenished within a human timescale.
• Examples include fossil fuels (coal, oil, natural gas) and nuclear energy.
• These resources cannot be replaced once depleted.
• Fossil fuels release greenhouse gases, contributing to climate change and air pollution.
• Nuclear power plants produce radioactive waste that requires long-term storage.

Types of Forces

• Force is a push or pull on an object with mass that causes a change in its velocity.
• Force is an external agent that can change an object's state of rest or motion; it has magnitude and direction.
• Force is measured in Newtons (N), where 1 N equals the force required to accelerate 1 kg by 1 meter per second squared.
• Forces can cause objects to speed up, slow down, change direction, or change shape.

Scalars and Vectors

• A physical quantity is something that can be measured.
• Scalar quantities have only magnitude (value).
• Vector quantities have both magnitude and direction, represented by arrows.
• The size of the arrow indicates magnitude.
• Force is an example of a vector quantity.

Contact Forces

• Contact forces act between objects that are physically touching.
• Tension is a pulling force exerted by a string, rope, or rod.
• Friction is a force that resists motion between two touching surfaces.
• Air resistance is a force that acts against the direction of movement of an object through the air; it increases with speed.
• Upthrust is an upward force on an object in a fluid (liquid or gas).
• Thrust is a driving force exerted by an engine.
• Normal reaction force is the balancing force exerted by a surface on an object pushing against it, acting at right angles to the surface.

Non-Contact Forces

• Non-contact forces act between objects that are not physically touching.
• Magnetic force acts on magnets or magnetic materials in a magnetic field, either attracting or repelling them.
• Electrostatic force acts on charged particles in an electric field, either attracting or repelling them.
• Gravitational force acts between masses, always pulling them towards each other

Measuring Forces

• A force meter (Newton meter) measures forces using a spring.
• Zeroing the force meter before use is important to avoid systematic errors.

Newton’s Laws of Motion

• Newton's first law states that an object will not change its motion unless a force acts on it.
• Newton's second law says the force on an object equals its mass times its acceleration.
• Newton's third law says when two objects interact, they apply forces of equal magnitude and opposite direction to each other.