Work Energy Theorem

Work Energy TheoremFeb. 19 & 20HW DUEN/ATonights HWRead & Study 8.3-8.6; do # 6-13 p. 119

LAB is due NEXT CLASS at the START OF CLASSDo Now20 minutes to work on your labs GO!10 minutes to complete #1-5!

Volunteers to share?

It increasedFriction, transfers of energy, etc.Volunteers to share?

If work is done on an object, the object acquires the ability to do workWhen work is done to raise a bowling ball, the bowling ball acquires the ability to do work on an object it hits when it falls.

9.3 Mechanical Energy

6When work is done to wind a spring mechanism, the spring acquires the ability to do work on various gears to run a clock, drive a car, ring a bell, or sound an alarm.9.3 Mechanical Energy

7Volunteers to share?

If work is done on an object, the object acquires the ability to do workSomething is acquired in order for an object to have the ability to do workThe something is MECHANICAL ENERGY2 types: PE & KELook at this:

8.4 POTENTIAL ENERGY, aka PE (pgs 106-107)An object may store energy by virtue of its positionThis energy that is stored and held in readiness is called potential energy (PE)In other words, this PE has the potential of doing work on somethingExamples:Compressed spring or stretched rubber band (tension)Electrical energy (battery)Gravitational potential energyGrav. PE = mgh The amount of gravitational potential energy possess by an object is equal to the work done against gravity in lifting it.

8.5 KINETIC ENERGY, aka KE (pg 108)KINETIC ENERGY IS NOT MOMENTUM!If an object is moving, then it is capable of doing workIt has energy of motion, or KINETIC ENERGYThe KE of an object depends on its mass and on its speedKE = m v2The KE of a moving object is equal to the WORK required to;Bring it TO that speed, from rest.orThe work the object CAN do while being brought to rest. The WORK-ENERGY THEOREMTHEN

ENERGYchanges

IFIF

WORKIs done

THENLike a wrecking ball!Not this one!!!! (Thats a train wreck)

Like a wrecking ball!This one!

Look at this:

Graphic Organizer (WRITE THIS!)THEN

ENERGYchanges

IFIF

WORKIs done

THENW = EGraphic Organizer (WRITE THIS!)THEN

ENERGYchanges

IFIF

WORKIs done

THENW = EMechanical Energy (M.E)Potential Energy (P.E)Kinetic Energy (K.E)Do #1-9!

18

P.EP.EP.EP.EP.E19

K.EK.EK.EK.E20In addition toWork Energy Theorem

Work Energy Theorem (both as a formula and in words, pg 108) Work changes energy If there is no change in energy, then no work is doneWork = the change in energy W = EIn addition toWork Energy Theorem

And the different types of PE & KE

Work Energy Theorem (both as a formula and in words, pg 108) Work changes energy If there is no change in energy, then no work is doneWork = the change in energy W = EIn addition toWork Energy Theorem

And the different types of PE & KE

There is one more MAIN CONCEPT for today

Work Energy Theorem (both as a formula and in words, pg 108) Work changes energy If there is no change in energy, then no work is doneWork = the change in energy W = ELaw of Conservation of Energy8.6: Conservation of Energy (p. 109-111)Energy itself cannot be seen, but the effects of it can be observed when energy TRANSFORMS from one FORM to another, Or TRANSFERS from one OBJECT to anotherEnergy cannot be created or destroyed only transformed or transferred.The TOTAL ENERGY AMOUNT does not change.TOTAL MECH. ENERGY = TOTAL P.E. + TOTAL K.E. M.E. = P.E. + K.E.MFMcGrawCh07 - Energy - Revised: 2/21/1025Conservation of EnergyExample: Energy transforms without net loss or net gain in the operation of a pile driver.

Part of the PE of the wound spring changes into KE. The remaining PE goes into heating the machinery and the surroundings due to friction. No energy is lost.Conservation of Energy

26Everywhere along the path of the pendulum bob, the sum of PE and KE is the same. Because of the work done against friction, this energy will eventually be transformed into heat.Conservation of Energy

27

5 MINUTES TO COMPLETE:

One is set up for you

And we are doing this one together

Now try this!

Skip a page

One is solved

Try this one!

Now Try this one!

0 JNow Try this one!

0 J- 400 JEXIT SLIP on scrapID:NAME:DATE:CLASS:Is it possible for an object to have both PE & KE simultaneously? EXPLAIN

What did you learn today that you are REALLY confident about?

What is confusing you?