Physics: Conservation of Energy & Gravitational Potential Energy

Energy Forms and Transformations

• Energy is neither created nor destroyed, only transformed from one type to another
• Types of energy: gravitational potential energy, kinetic energy, radiant energy, chemical energy, electrical energy, nuclear energy

Gravitational Potential Energy

• Depends on an object's height
• Calculated by the equation: GPE = mgh (mass x acceleration due to gravity x height)

Kinetic Energy

• Depends on an object's movement
• Calculated by the equation: KE = 1/2 mv^2 (one half x mass x velocity squared)

Radiant Energy

• Can travel through empty space (vacuum)
• Comes in the form of electromagnetic radiation and gravitational radiation
• Examples: sunlight, gamma rays, radio waves
• Travel at the speed of light (~300,000,000 m/s in a vacuum)

Chemical Energy

• Stored in the bonds of chemical compounds
• Released or absorbed through chemical reactions
• Examples: photosynthesis, batteries, hand warmers, petroleum

Electrical Energy

• Caused by moving electric charges
• Measured in Joules
• Can be kinetic or potential energy
• Examples: moving electrons in a wire, lightning, batteries

Nuclear Energy

• Released from the nucleus of atoms
• Through fission (splitting atoms) or fusion (combining atoms)
• Examples: nuclear power plants, stars like the Sun

Heat Capacity

• The minimum heat absorbed by a substance before a unit change in temperature
• Specific heat capacity: for one gram of a substance
• Molar heat capacity: for one mole of a substance
• Examples: water has a high specific heat, metals have low heat capacity

Energy in Living Organisms

• Energy is required for survival and reproduction
• Energy from the sun is transformed into usable forms for living organisms
• Examples: photosynthesis, cellular respiration, ATP

Vibrations and Waves

• Repeated back-and-forth motion of a particle
• Characterized by periodic motion
• Examples: sound waves, light waves, ocean waves

Sound Waves

• Vibrations that travel through a medium (solid, liquid, gas)
• Speed of sound depends on the medium
• Frequency, wavelength, amplitude, period, and speed are related
• Examples: music, voice, echoes

Electromagnetic Spectrum

• Range of frequencies of electromagnetic radiation
• Includes: radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, gamma rays
• Each type has a specific frequency and wavelength

Color and Light

• Electromagnetic radiation with a frequency visible to the human eye
• Visible spectrum: red, orange, yellow, green, blue, indigo, violet
• Each color has a specific frequency and wavelength

Reflection of Waves

• Change in direction of waves when striking a surface
• Incident ray, reflected ray, and normal line are related
• Law of Reflection: angle of incidence equals angle of reflection

Interaction of Light with Objects

• Opacity: blocking of light
• Transparency: transmission of light
• Translucency: partial transmission and bending of light
• Examples: mirrors, glass, frosted glass

Refraction

• Bending of waves when passing from one medium to another
• Snell's Law: ratio of angles of incidence and refraction equal to ratio of indices of refraction
• Examples: prisms, lenses, total internal reflection### Doppler Effect
• When an ambulance siren is moving towards an observer, the observer perceives a higher pitch sound, and a lower pitch when it is moving away.
• A sonic boom occurs when a sound source is traveling faster than the speed of sound, an extreme form of the Doppler effect.
• Edwin Hubble used the Doppler effect in light emitted by distant galaxies to conclude that the universe is expanding.
• An observer will perceive a blue shifted galaxy when it is moving towards them, and a red shifted galaxy when it is moving away.

Properties of Light

• Properties of light include intensity (or brightness), direction, frequency (or color), and polarization.
• Light travels in straight lines, bounces symmetrically from mirrors, and can be colored (like a laser).
• White light contains a full rainbow inside it.

Reflection and Refraction

• Reflection is when light bounces off a shiny, reflective surface.
• Refraction is when light bends when moving from one medium to another.
• The law of reflection states that the incident angle is equal to the reflected angle.
• Refraction occurs due to density changes, causing a gradual bend in light.

Diffraction

• Diffraction is the process by which a beam of light is spread out as it passes through an aperture or across the edge of an object.
• Overlapping light waves create an interference pattern with light and dark areas.
• Constructive interference occurs when peaks or troughs of two waves meet, resulting in a light area.
• Destructive interference occurs when the peak of one wave meets the trough of another, resulting in a dark area.
• A single slit produces a diffraction pattern with a large central maximum and alternating bands of dark and light.
• Thinner apertures lead to more diffraction, with the pattern getting dimmer towards the edges.

Electric Power

• Electric power represents the ability of an electric source to supply or of an electric device to consume electric energy over a specific time period.
• Electric power is measured in watts (W), with 1 W equal to 1 joule per second.
• Electric devices and appliances have a label showing their electric power.
• Electric power can be calculated by multiplying current by voltage, or by multiplying current by resistance, or by dividing work done by time.

Electric Circuits

• An electric circuit is a complete loop in which electrons from a voltage or current source flow.
• The current in the circuit is the rate of flow of charge, measured in amps.
• Components in a circuit, such as bulbs, sensors, and motors, act as resistors, resisting the flow of charge.
• Resistance is voltage divided by current, so adding resistors decreases the current.

Voltage Sources

• Voltage sources provide energy to electrons in an electric circuit.
• Batteries are a type of voltage source that convert chemical energy into electrical energy.
• Generators use moving magnets and electromagnetic induction to generate voltage.
• Different types of voltage sources, such as nuclear, coal, natural gas, hydroelectric, and wind power, all convert energy into electric energy.