TAKS objective 4Energy, Forces, and Motion

Middle School ScienceScience TAKS Need to Know

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Energy

The ability to do work or to cause

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Chemical Energy – Energy transformations

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Chemical energy – when light energy from the sun is converted to the energy in the bonds of the sugar molecules formed in photosynthesis.

Chemical Energy

Examples of chemical energy changing into heat energy:

Lighting a matchBurning a wood fire

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Heat energy- Energy transformations

• Heat energy – energy is absorbed and temperature rises.

• Specific heat- the ability of a substance to absorb heat energy

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Specifics of Specific HeatSpecific heat capacity of water is larger than soil,

so the rise of temperature is less for water, all other things being equal.  But, there's anothereffect:

Sun's energy penetrates farther into water thanit does into earth, so the temperature rise persquare meter of exposed surface  is less forwater.

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Temperature is a measure ofthe average kinetic energyof the molecules in the object.-----------------------------------------Will both fingers feel the same temperature when they'reput in the warm water?

Water Holds Thermal Energy at Lower Temperature

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Electrical energy- Energy transformations

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Electrical energy- flow of electrons (a current)

Other ways of generating electricity:

•Water flowing through a dam in a river to move turbines

•Wind generators that use the energy of moving wind & operate a generator

•Nuclear power plants convert atomic energy into heat. Heat boils water to form steam & then follows the same energy transformations as coal power plants

Many energy transformations…

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Electrical to mechanical:

Electricity used to spin the CD (Spinning CD has mechanical energy due to its position or motion)

Electrical to sound:

A laser converts the digital information on the CD into electrical energy and this energy goes to the headphones as a vibration- this transmits Sound!

Chemical to electrical:

Batteries store chemical compounds that react when they are used to power something. This produces a flow of electrons which is electricity!!

Sound energy- Energy transformations

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Sound – consists of mechanical energy waves created by vibrations.

Sound must travel through something (called “medium” or “media”) such as air, water, or a solid.

The medium carries the energy of the wave from one place to another.

Example: Air transmits the energy of the vibrating material in the headphones to your eardrums.

A vacuum is a space that contains little or no matter. Sound can’t travel through a vacuum since there are no particles to squeeze together (compression) or spread apart (rarefaction)

Many times it takes a whole series of energy conversions to do a certain job. For example, just to get the energy to make a piece of toast, there are several energy

conversions involved.

• Chemical energy stored in coal is released as heat and light energy when the coal is burned. The heat energy is used to produce steam and is changed into mechanical energy in a generator. The generator converts mechanical energy into electrical energy that travels through power lines into your home. When you use your toaster, that electrical energy is again changed into heat energy.

• Have you ever touched a light bulb when it was on? Or tried to change it when it burnt out after being on? What you have discovered is the conversion process of energy- When you turn on a light, not all of the electricity is converted to light energy. Some of the energy is converted to heat.

Remember, energy is never lost- it’s only converted from one form to another.

This is the law of conservation of energy

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Light waves do not need a medium to transmit energy! They can even travel through empty space.

A wave is a disturbance that transfers energy from one place to another.

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Water waves are a form of a wave that transmits mechanical energy across the surface of water.

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Seismic waves are caused by earthquakes that transmit mechanical energy through the Earth’s layers.

Potential (PE)

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Stored energy

Kinetic Energy (KE)

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Energy due to motion of an object

Speed & mass affect kinetic energy–

Faster/heavier…more Kinetic Energy

Did you know that Did you know that the gas burned in a the gas burned in a car engine is car engine is chemical energy chemical energy being turned into being turned into Kinetic Energy?Kinetic Energy?

Rubber band flying through the air has kinetic energy

Before the yo-yo begins its fall it has stored energy due to its position. At the top it has its maximum potential energy. As it starts to fall the potential energy begins to be changed into kinetic energy. At the bottom its potential energy has been converted into kinetic energy so that it now has its maximum kinetic energy

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A waterfall has both potential and A waterfall has both potential and kinetic energy. The water at the top kinetic energy. The water at the top of Bridal Veil Falls has stored of Bridal Veil Falls has stored potential energy. When the water potential energy. When the water begins to fall, its potential energy is begins to fall, its potential energy is changed into kinetic energy. changed into kinetic energy.

This change in energy also This change in energy also happens at Niagara Falls where it is happens at Niagara Falls where it is used to provide electricity from the used to provide electricity from the transformation of mechanical and transformation of mechanical and electromagnetic energy.electromagnetic energy.

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Energy TransformationsPotential energyA rock sitting at the

top of a cliffRoller coaster car at

the top peak of a hill

A swimmer posed to dive off the end of a diving board

NO MOTION !!

Kinetic energyA bouncing ballA moving roller

coaster A track star runningA girl skiing

MOTION is the key!!!!

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Forces may MOVE objects

Forces may transfer

energy between objects

A book resting on a desk illustrates balanced forces. However, a book dropped from a desk illustrates unbalanced forces. In this case, gravity has overcome the balance of forces.

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You use force to move your body

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When you bend your arm, your muscles contract, which applies force to your arm bones. Your arm responds to this force by moving.

During breathing, muscles contract (use force) to move air in and out of the lungs.

The heart contracts (uses force) to pump blood through the blood vessels, carrying oxygen to the muscles.

All living things use force to move

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Emerging seedlings exert force on the surrounding soil.

This force pushes the stem of the plant out of the ground.

Plants exert force to open flower petals, curl & uncurl leaves & push roots through the soil.

Force is used to move materials in & out of cells.

Fish exert force to swim by pushing against the water.

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In order for a force to move something, it must be an unbalanced force. This means that a force is

stronger in one direction than the forces in the opposite direction.

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Acceleration of an object moving in one direction is the speed (m/s) per unit of time (s), or change in speed divided by time. The unit for acceleration is m/s2.

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Data can be displayed & interpreted in many

ways

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Force & motion are related

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What’s the advantage to knowing how much force we use to do something???

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A lever is a bar that rests on a support called a fulcrum which lifts or moves loads.

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Types of levers

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A pulley is a simple machine that uses grooved wheels and a rope to raise, lower or move a load. When a rope passes over a wheel, it changes the direction of effort (pull) needed to move the load.

This pulley has 1 wheel, so it changes the direction of pull 1 time. The input force is the same as the weight using the pulley.

Wedge

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A wedge is an object with at least one slanting side ending in a sharp edge, which cuts material apart.

An inclined plane is a ramp used to reduce the effort needed to raise or lower an object over a vertical height.

It is easier to climb stairs to get to a second floor than to climb straight up a rope. It is easier to walk up a long, gentle hill than to climb up a short, steep hill.

Examples of inclined planes:Loading ramp; Stairs or wheelchair rampMountain road; Threaded screw.

The ancient Egyptians used inclined planes, or ramps, to move huge blocks of stone to build the pyramids.

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A screw is an inclined plane wrapped around a pole

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Wheel & axle

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A wheel with a rod, called an axle, through its center lifts or moves loads.