LEARNING OBJECTIVE O' THE DAY:

I will be able to calculate instantaneou and average power after today

's class.

WORDS O' THE DAY:

• Work (Force through displacement)
• Dot Product ("scalar product")
• Work ("Newton meter (Nm)" or "Joule (J) ")
• Hooke's Law (F = -kx)
• Work done by or done on a spring = 1/2k_ix² - 1/2k_fx²
• Kinetic energy of an object in motion = 1/2mv²
• Potenial energy in a compressed spring = 1/2kx²

CALENDAR:

WORK/ENERGY Test coming on Thursday

WORK O' THE DAY:

PRESENTING -- the first annual (?) creative writing physics awards!!!

And the winners are poster #5 submitted by team "We Are Jake"

Please come up and claim your rewards!

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Let's check your homework-- these 3 lucky folks will come up and present their responses to those 3 problems (26, 32, 38):

Now let's grab a quick sheet of paper with your name, period & date:

1) What is the formula for potential energy on a spring?

2) Why are there two formulas that we can use to calculate the kinetic energy of a spring?

3) Why is it improper to discuss friction in a system where energy is simply transferred between types (KE => U for example)?

4) What is the definition of average power?

5) What are the SI Units for power?

6) What are the SI Units for work?

7) What are the SI Units for energy?

8) What conditions must exist in order for the derivative of potential energy (with respect to motion in one direction such as "x") to = the negative of the force applied?

9) Give an example of a conservative force.

10) Give an example of a non-conservative force.

11)  You are working on a complex problem involving a compressed spring, kinetic energy, gravitational potential energy and energy lost to friction. NO outside forces are acting on that system.

Using words ONLY, describe that situation using energy considerations.

12) Consider the following situation: You are working to solve a problem involving gravitational potential energy turning to kinetic energy and NOT ignoring friction. You keep coming up with an expression that shows that increasing friction INCREASES the speed of the object in question.

Suggest a likely error that you made that ends up with increasing instead of decreasing kinetic energy.

Now let's review

If time permits, find a problem in the book where outside forces ARE present.

HOMEWORK (est minimum time: 40 minutes at home):

• problems 26, 32, 38