LEARNING OBJECTIVES:

1) I will be able to show that work must be done on an object to change the energy of the object during today's class (Let's have a group post this for us *somewhere* in the room today)

WORDS O' THE DAY:

• Work (Force through displacement)
• Kinetic Energy (Energy of Motion)
• Law of Conservation of Energy (In our daily lives, Energy is never created or destroyed, it just changes form)

FORMULAE OBJECTUS:

Work = ∆E = Fd = Fdcosθ

KE = 1/2mv²

WORK O' THE DAY:

How was your break? Please converse with your team!

Now let us review our test results. WE DID GOOD!!!!! (I Was kinda nervous about the graphing part but we did GOOD ON THAT ONE TOO!)

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• Work is defined to be the force exerted on (or by) an object through a displacement

Sooooo.... let's go back to our meteor. When we look up at night and see a shooting star, is that meteor bigger, smaller or about the same size as our 1.0 kg chunk in our opening?

How does our definition of work apply here?

Now let's take a gander at the Russian meteorite (remember that from middle school?

It may interest you to know that meteor traveled hundreds or even thousands of miles during that video.

Yes, it did hit the ground in Siberia, but far away from any people. To my knowledge there isn't any video of it actually striking the Earth

Now let's talk about THE BIG ONE!

So... a big ol rock about 5.0 miles in diameter with a MASSIVE mass of millions of tons smacks into the atmosphere going 11,000 m/s or so.

What happens when it hits the Earth?

Where does all that KE go?

Since we've no doubt got a bit more time, let's jump to Work & Energy 01

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Can work be negative? Please discuss.

Let's say your 3rd cousin (twice remmoved) pulls your kid sister (m = 35 kg) on a sled across a frozen pond witha force of 101 N for a displacement of 202 meters to the west.

Sketch that situation

What additional information do you need to determine the amount of work your cousin produced during that event?

What information provided is irrelevent for this problem.

• Why is that?
• Will that always be the case?

Please discuss

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Uh oh! There's a hole in the ice dead ahead. You go rushing to the rescue and you and your cousin have to exert <HOW MUCH?> FORCE on that sled to stop it in 5.50 meters before your sled (and your sister) plunge into the icey waters?

How does this problem relate to our learning target?