Ch 8

Ch 8 Feb 24

HW Due #6-13 & Lab **Place both of these in In Box!**

Tonight’s HW

Read & Study 670-672. Complete #1-7 on p. 672 (write FULL Q & A – they are typed on website if you prefer!) Also, finish today’s notes if you don’t during class!Ch 8 test on March 4

Do Now Take one Read the 1st column.Complete the 2nd

Do Now Complete the 3rd column. You have all class to think about your response for the last column – that will be your exit for today (in addition to the back of this paper)

http://www.youtube.com/watch?v=rMBpuQMj1Qw

RECAP - In addition to…Work 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 done

Work = the change in energy W = EΔ

In addition to…Work 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 done

Work = the change in energy W = EΔ

In addition to…Work 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 done

Work = the change in energy W = EΔ

Law 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… o TRANSFORMS from one FORM to another, o Or TRANSFERS from one OBJECT to another

Energy 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.

Conservation of EnergyExample: Energy transforms without net

loss or net gain in the operation of a pile driver.

MFMcGraw Ch07 - Energy - Revised: 2/21/10 8

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

Everywhere 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

5 MINUTES TO COMPLETE:

One is set up for you…see the board

But you need to complete it!!!

KE = ½ (15 kg) (10 m/s)2

Using GERMDOS, there are a few ways to manipulate the numbers to get to the correct answer. I think the easiest way is this:

KE = (7.5 kg) (100 m2/s2)KE = 750 kg m2

s2

KE = 750 J

Complete the next 2!750 J

3000 J*Notice – we doubled the velocity

(compared to #1)…did the KE

double?

1500 J*Notice – we doubled the velocity

(compared to #1)… …did the KE

double?

Skip a page…

One is solved…

Try the rest!

PE = mghPE = (1 kg)(10 m/s2)(0m)

PE = 0 J

PE = mghPE = (1 kg)(10 m/s2)(0m)

PE = 0 JPE = mghPE = (10 kg)(10 m/s2)(-4m)

PE = -400 J

PE = mghPE = (1 kg)(10 m/s2)(0m)

PE = 0 JPE = mghPE = (10 kg)(10 m/s2)(-4m)

PE = -400 J

PE = mghPE = (15 kg)(10 m/s2)(-7m)

PE = -1050 J

Go back…And finish this entire packet!!! (including the page we skipped)

Anything not done in class is HOMEWORK!

Check in at STOP SIGNS!

Your HWFinish today’s notes –

the ENTIRE PACKET. Due at the start of next

class!!!

Read & Study 670-672. Complete #1-7 on p. 672 (write FULL Q & A – they are

typed on website if you prefer!)

Also, finish today’s notes if you don’t during class!

Ch 8 test on March 4 Study guide is online this

afternoon, and will be passed out on Wednesday

EXIT SLIPFinish the last column & back of your Do Now – turn in!

Turnpaper over