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Ms. Brown 8th Grade General Science Jennifer C. Brown.
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Transcript of Ms. Brown 8th Grade General Science Jennifer C. Brown.
Ms. BrownMs. Brown8th Grade General Science8th Grade General Science
Jennifer C. Brown
Energy is the ability to “do work” and describes the ability of things to change or cause change in other things. • Work is done when a force moves an object over a
distance.
Jennifer C. Brown
You do 1 joule of work if you push with a force of 1 newton for a distance of 1 meter.
Jennifer C. Brown
(joules- J) (N) (m)
Jennifer C. Brown
How much work is done by a person who pulls a cart with a force of 50 newtons if the cart moves 20
meters in the direction of the force?
Jennifer C. Brown
The origin of energy in the universe is unknown.
• Most Scientists think it was created
during the big bang.
Scientists believe that the total amount of energy and matter in the universe is constant. *What does this mean?*
Jennifer C. Brown
This law states that energy can be neither created nor destroyed. It can
only be transformed from one type into one or more other types of energy (heat
may be released).
Electrical Energy
Mechanical Energy (Sound)
Jennifer C. Brown
1) Mechanical Spinning Fan
2) Chemical Burning Candle
3) Nuclear Nuclear Reactor
4) Heat Toaster
5) Electrical Generator
6) Light Lamp (bulb)
Jennifer C. Brown
Question: Where Does Candle Wax Go?
Answer: Have you ever noticed how you have less candle after burning than before? This is because the wax oxidizes (burns) in the flame to yield water and carbon dioxide, which dissipate in the air around the candle, in a reaction which also yields light and heat. Jennifer C. Brown
Based on what we know about energy, machines allow us to do incredible things.
A machine is a device with moving parts that work together to accomplish a task.
Initially, we invented simple machines like levers to
accomplish tasks.Jennifer C. Brown
Mechanical energy is the energy with which moving objects perform work.• Hammer striking a nail• Jack lifting a car• Pedals turning wheels of bicycle• Sound• You striking a match
Jennifer C. Brown
Sound Energy:• Sound is a form of energy produced by a
vibrating object. • When an object vibrates, it moves rapidly
back and forth, moving (expanding & compressing) the air around it and forming sound waves.
Jennifer C. Brown
• The substance that sound travels through is called the medium.
• Can sound waves travel through a vacuum? No, because there are no particles to transmit it.
• Similar to light, in what form do you think sound travels in? Waves
Jennifer C. Brown
Important Parts of a Wave:
• Wavelength – the distance from one point in a wave to a corresponding point in the next wave.
• Amplitude – the height of the crest measured from the undisturbed surface.
• Frequency – the number of waves that pass by a fixed point in a given amount of time.
Jennifer C. Brown
2 Main types of waves:• Transverse Wave – vibrates up and down at
a right angle to the direction in which the wave is traveling. ( shown by a rope moving up and down).
• Longitudinal Wave – vibrates back and forth within its direction of travel.
Jennifer C. Brown
Chemical energy is the energy stored in certain substances because of their chemical makeup. (ex. = batteries, foods, propane gas)
Jennifer C. Brown
The energy stored within the nucleus of an atom. This energy can be released by joining atoms together or by splitting atoms apart.
Jennifer C. Brown
The energy produced by the molecular motion of matter. (ex. – rubbing hands together, burning a match..)
Jennifer C. Brown
Produced by the flow of electrons through a conductor, such as a wire. (ex. – computers, televisions …)
Jennifer C. Brown
A form of radiant energy that moves in waves. (ex. – magnifying light, laser eye surgery…)
Jennifer C. Brown
Potential Energy:• The stored energy
of an object as a result of its position.
Kinetic Energy:
• The energy of motion (vertical or horizontal) Jennifer C. Brown
Equations:Equations:• Potential Energy
(in Joules)
EEpp = m = m xx g g xx h h
mass (m) mass (m) xx gravity (g) gravity (g) x x height (h)height (h)Jennifer C. Brown
• Kinetic Energy (in Joules)
EEkk = ½mv= ½mv22
mass (m) mass (m) xx velocity (v) velocity (v)Jennifer C. Brown
The speed of sound depends primarily on what 2 factors?
• The medium through which it is passing Denser medium = faster speed of sound
• The temperature Colder temperature = faster speed of sound
Jennifer C. Brown
Number the mediums from fastest speed of sound to lowest speed of sound:
Medium State
Iron Solid
Water Liquid
Air Gas
Glass Solid
Jennifer C. Brown
Light is a visible form of energy.Light is a visible form of energy.• Travels in waves• Travels in straight paths called rays• Unlike sound waves, however, light rays cannot
bend around objects.• When light strikes a surface:
Reflected Absorbed Transmitted
The smoother the surface, the more The smoother the surface, the more accurate the reflection. (mirror)accurate the reflection. (mirror)Jennifer C. Brown
Transparent Materials:Transparent Materials:• Ex – window glass• Permit almost all of the incoming light to pass through.
Translucent Materials:Translucent Materials:• Ex – wax paper• Let some light pass through but scatter the light so it isn’t
clear.
Jennifer C. Brown
RefractionRefraction• When light waves are
bent when passing through two media of different densities, such as from water into air.
• This is how a lens is made.
Jennifer C. Brown
A LensA Lens• A piece of transparent glass or plastic that has
curved surfaces. Convex Lens – (surface curves outward) Bends light rays
so they are focused in toward a common point. Concave Lens – (surface curves inward) Bends light rays
so they spread out.
Jennifer C. Brown
The Electromagnetic SpectrumThe Electromagnetic Spectrum• Light waves are a part of a larger group of
energy waves that can travel through a vacuum called electromagnetic waves.
• Electromagnetic Waves: Radio waves Microwaves Infrared waves Visible light Ultraviolet rays X rays Gamma rays
Jennifer C. Brown