Introduction to Waves

Force, Motion and Energy Reporting Category 2

Wave A wave is any disturbance that transmits energy through matter or space.

Basic properties of waves Basic properties of waves : Energy is transferred from one place to another in a wave motion. (Example: a tidal wave is an energy wave) Only the shape or form of wave travels, not the substance it travels through called the medium.

Amplitude (A) Amplitude – height of a wave.

Wave Length ( ) Wave Length – distance from one wave to the next by measuring: *crest to crest *trough to trough *midpoint to midpoint

Wave Frequency (f) Frequency – The rate at which the crest passes a given point. Unit for frequency is the Hertz (Hz). Hertz – how many waves go by per second.

Frequency Continued High frequency has short wave length. Low frequency has long wave length

Using the Wave Equation Speed = wave length x frequency

What is a wave? It is the way in which energy is transferred from one place or object to another. Waves come in various forms. Waves can travel through a variety of materials or even empty space. Waves can do work, sustain life, or cause great destruction; this occurs when the energy of the wave is absorbed by matter.

When we think of waves, most of us think about the beach. These waves travel through water. In this case, water is called the medium.

The medium can be a gas, such as when sound travels through the air.

The medium can be a solid, such as when an earthquake shakes California.

Then there are light waves that require no medium at all. They are called electromagnetic waves

Forms of

Energy is the ability to cause change

Energy has no mass or weight Energy does not take up space Energy is NOT matter Energy vs. Matter everything on Earth is either energy or matter Matter has mass and weight Matter takes up space Matter is NOT energy

THERMAL ENERGY energy due to molecular movement within an object increased temperature = increased thermal energy

Which of these objects has more thermal energy?

CHEMICAL ENERGY Chemical energy is stored in chemical bonds. When molecules are broken apart energy is released.

Each of these items contains chemical energy.

LIGHT ENERGY Energy carried by light is called radiant energy. Light energy travels at a speed of 300,000 km/s.

ELECTRICAL ENERGY energy of electrons moving along a path (electrical current)

NUCLEAR ENERGY energy stored in the nucleus of an atom

POTENTIAL ENERGY Energy an object has because of its position

KINETIC ENERGY Energy of motion. Only a moving object has kinetic energy Amount of energy depends on speed and mass

POSITION 1 POSITION 2 POSITION 3 Potential Energy Kinetic Energy Potential Energy The boulder is in a resting position with low potential energy and no kinetic energy. EXAMPLE 1 The boulder at the top of the hill has potential energy and no kinetic energy. As the boulder rolls down the hill, the potential energy transforms into kinetic energy and kinetic energy becomes greater until

Examples of Energy Transformations Your body converts chemical energy in food into energy …. it needs to move,think,grow and heat the body.

What is temperature ?

Moving Molecules All matter in the Universe is made of atoms that are on the move all the time!

How fast atoms move gives us our states of matter. In a solid, the atoms are tightly packed together. They cannot change position easily. They can only vibrate in place. Solids have a definite shape & definite volume.

In a liquid, the atoms are able to slide past each other. They can easily change positions in the liquid. Liquids have a definite volume but not a definite shape.

In a gas, the atoms are much farther apart than in solids or liquids. They have plenty of space to move around in. They can easily spread throughout all the space in the container that they are within. Gases do not have a definite shape or a definite volume.

Boiling is when heat is added to water in liquid form (when it’s molecules are moving very rapidly!) Water vapor (steam) is produced. When this occurs, water goes from the liquid state to the gaseous state. This is known as VAPORIZATION.

Solidification or freezing is due to a lack of heat in liquids (when it’s molecules are moving very slowly!) Ice and other solid forms of water are produced when this process takes place.

CONDENSATION is defined as the conversion of a substance (like water) from the vapor state to a denser liquid state that is initiated by a reduction in temperature of the vapor. This process is responsible for the formation of clouds. Condensation is also a vital component of the water cycle for clouds then create rain.

Melting is the process by which heat is added to water (or any liquid substance) in its solid state such as ice. The ice then turns into liquid water.

Force, Speed, and Motion How are they related?

Kinds of Force There are many different kinds of force. There are pushes and pulls electromagnetic forces weak forces strong forces and gravitational forces, Some forces are referred to as contact forces and some are non-contact forces

Weight is a type of force Weight is the result of the force of gravity pulling on a mass. The greater the force of gravity, the greater the weight. Mass is a measure of how much matter an object contains.

Acceleration

F=ma is Newton’s 2nd Law and can be stated: A net force is equal to the mass of the object times its acceleration. Therefore if equal force is applied to two objects of different mass, the smaller mass will accelerate more

If an object is traveling at a constant speed but is going in a circle, it is accelerating because its direction is changing

Are these objects accelerating? Explain.

Newton’s Second Law Little Force Big Force Little Acceleration Big Acceleration Same Mass

Same Force Small Mass / Big Acceleration Big Mass / Small Acceleration

Simple Machines Levers Inclined Plane

Simple Machines Wheel and Axle Pulley

Simple Machines Wedge Screw

Machines Cannot… Decrease the amount of work necessary to accomplish a given task Have 100% efficiency Run perpetually

Machines Can… Make work EASIER to accomplish (but amount is the same) Change magnitude of force required to accomplish task Change direction of force required to accomplish task

Forces related to basic processes Blood flow in the body Plate movement (tectonics) – Volcanic eruptions – Earthquakes – Mountain building Emergence of seedlings Erosion

Blood Flow

Volcanic Eruptions

Hilo, Hawaii

Mountain Building

Emergence of Seedlings

Erosion

Check your understanding

1. How do the wave lengths compare for two waves traveling at the same speed with frequencies in a ratio of 2 to 1? A) 2:1 B) 1:2 C) 4:1 D) 1:4

2.The boulder would have the greatest kinetic energy at which of the positions on the waterfall? B A position 1 B position 2 C position 3 D position

3.A yo-yo can demonstrate both potential and kinetic energy. When does a yo-yo have it greatest potential energy? A In the hand before the yo-yo is released B At the bottom of the string C When the yo-yo is falling D When the yo-yo is climbing the string

4. Which of the following is an example of a wave? a. erosion b. an earthquake c. a volcano d. a glacier

5. Windmill farms are becoming a popular method of generating electricity for some communities. What form of energy in wind is used to turn the giant blades of the windmill? A.Chemical B.Mechanical C.Electrical D.Thermal

6.In a nuclear reactor, the energy used to turn water into steam is in what form? A. Chemical B. Nuclear C. Electrical D. Thermal

7. Which of the following can be used to transform chemical energy into heat energy? Answer: B A. melting a candle B. lighting a match C. solar panels D. light bulb

8.When the human heart contracts, it pumps blood to other parts of the body. When the heart contracts, the blood moves because the- - A. Pressure to the heart increases B. Temperature of the blood increases C. Density of the blood increases D. Size of the heart increases

9.As a lima bean seedling starts to grow into the soil the root tip is able to push through the soil because it acts as a -- A. Wheel B. Pulley C. Gear D. Wedge

10.Which force causes the water to move downstream? A. Gravitational B. Chemical C. Electrical D. Solar

11. Which of the following describes the motion of the runner? A The runner is moving at a constant rate B The runner is moving slower at the end C The runner is speeding up D The runner’s speed was a constant 4 m/s