THE ABILITY TO CAUSE CHANGE ENERGY THE ABILITY TO CAUSE CHANGE

Relate transformations and flow of energy within a system-chemical, mechanical, electromagnetic, light, sound, thermal, electrical, and nuclear. Goals Identify energy transformations within a system (e.g. lighting of a match). Sound

Types of Energy mechanical energy

Heat energy -transfer of thermal energy Types of Energy Thermal energy - due to temperature (recall that this comes from the motion of molecules, so it is really kinetic energy) Heat energy -transfer of thermal energy Chemical Potential Energy - stored in chemical bonds Nuclear energy - stored in the nuclei of an atom Electrical energy - EM interactions Radiant energy -carried by EM waves

Energy CLIP Energy is the capacity (ability) to do work. Potential Energy: Present in an object that has the potential to move because of its position Kinetic Energy: Associated with an object in motion

Potential and Kinetic Energy

How tall should they make they make the 1st hill? Question An amusement park wants to build a new roller coaster. They want the 2nd hill to be 65m tall. How tall should they make they make the 1st hill? What information do we still need?

Kinetic Energy the mass (m) of the object the speed (v) of the object. Motion KE of an object depends upon two variables: the mass (m) of the object the speed (v) of the object.

Calculating Kinetic Energy A formula to find the kinetic energy of any body based on its velocity.

Unit for Energy (add everything in blue to 1st page) The Joule (J) is the SI unit of Energy. The calorie is another common unit for energy Where does this come from? (KE = ½ m v2) 1J= 1N●m

Example Problems Kinetic Energy (KE = ½ m v2) 1) The velocity of a car is 65 m/s and its mass is 2515 kg. What is its KE?   2) If a 30 kg child were running at a rate of 9.9 m/s, what is his KE?

Practice Problems IN THIS ORDER…. Page 2: #s 6, 7, 8, 5

Potential Energy An object can store energy as the result of its position. Clip

Potential and Kinetic Energy Click photo

Forms of potential energy Gravitational Elastic Chemical -position above the Earth’s surface -stored in something stretchy -chemical reaction

Gravitational Potential Energy GPE is the energy stored in an object as the result of its vertical position (i.e., height). Amt. of GPE is dependent on two variables: the mass the height

Calculating Gravitational Potential Energy GPE = mgh

Elastic Potential Elastic PE is the energy stored in elastic materials as the result of their stretching or compressing.

Conservation of Energy

Conservation of Energy Energy cannot be created or destroyed…only changed from one form to another. The total energy of an isolated system remains constant (isolated systems have no external forces and no mass changes)

ENERGY BEFORE = ENERGY AFTER Energy can be changed from one form to another, but it does not disappear.

Conservation of Energy

Conservation of Energy TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME Tutor Vista Activity (click)

TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME Conservation of Energy KEi + PEi = KEf + PEf TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME

Conservation of Mechanical Energy: KEi + PEi = KEf + PEf Problem: A student lifts his 2.0 kg pet rock 2.8 m straight up. He then lets it drop to the ground. Calculate the following: How much Potential Energy does it have at the top (before he drops it). How much Kinetic Energy does it have at the top (before he drops it). After it is dropped, how much KE will it have when it is 1.4 m above the ground? Total=54.88 54.88 = PEf + KEf 54.88 = mgh + KEf 54.88 = (2) (9.8)(1.4) + Kef 54.88 =27.44 + KEf 27.44 J = KEf 54.88 J 0 J

Conservation of Mechanical Energy: Conservation of ME only hold true when the only energies of the system are KE and PE. Therefore, in the presence of friction energy is transformed to other types of energies.

Tutor Vista Activity (click)

Examples 21 Lighting a Match Steam Engine Battery Can you think of More? ENERGY PROJECTS

What happens when it hits the ground? Where did the energy all go?

As it is falling and when the object hits the ground the energy is converted into other types of energy such as: sound energy (waves), Light Energy (sparks), thermal energy due to friction (heat) in the ground and air, vibrations in the earth (energy waves.) If the object bounces, some energy is converted momentarily into elastic potential energy.

EOCT Questions Which statement about energy is true? A Energy can be increased in a closed system. B Energy cannot be conserved. C Energy can be decreased in a closed D Energy cannot be created nor destroyed.

Wile E Coyote & Roadrunner Clip