DAY 40

#Goals: SWBAT...

1. Write & understand the equations for Total Mechanical Energy

2. Understand the relationship between work and power

3. Solve basic work & power problems

I'm not checking Day 39 HW today. If you'd have a deep, burning desire to turn it in, I'll give extra credit for it tomorrow.

Warm-Up (4min): The Flow of Mechanical Energy

• Read, then complete.
• Mechanical energy is the energy that is possessed by an object due to its motion or due to its position. Mechanical energy can be either kinetic energy (energy of motion) or potential energy(stored energy of position).
• An object that possesses mechanical energy is able to do work

• A classic example involves the massive wrecking ball of a demolition machine. The wrecking ball is a massive object that is swung backwards to a high position and allowed to swing forward into building structure or other object in order to demolish it. Upon hitting the structure, the wrecking ball applies a force to it in order to cause the wall of the structure to be displaced. The diagram below depicts the process by which the mechanical energy of a wrecking ball can be used to do work.

• Give three more examples of scenarios in which an object uses mechanical energy to do work

CLASSWORK

1. #040A: Total Mechanical Energy Notes

The Total Mechanical Energy

As already mentioned, the mechanical energy of an object can be the result of its motion (i.e., kinetic energy) and/or the result of its stored energy of position (i.e., potential energy). The total amount of mechanical energy is merely the sum of the potential energy and the kinetic energy. This sum is simply referred to as the total mechanical energy (abbreviated TME).

TME = PE + KE

As discussed earlier, there are two forms of potential energy discussed in our course - gravitational potential energy and elastic potential energy. Given this fact, the above equation can be rewritten:

TME = PEgrav + PEspring + KE

The diagram below depicts the motion of Lee Ben Fardest (esteemed American ski jumper) as he glides down the hill and makes one of his record-setting jumps.

Look at the starting and ending energies. Is energy conserved in this example?

The total mechanical energy of Lee Ben Fardest is the sum of the potential and kinetic energies. The two forms of energy sum up to 50 000 Joules. Notice also that the total mechanical energy of Lee Ben Fardest is a constant value throughout his motion. There are conditions under which the total mechanical energy will be a constant value and conditions under which it will be a changing value. This is the subject of Lesson 2 - the work-energy relationship. For now, merely remember that total mechanical energy is the energy possessed by an object due to either its motion or its stored energy of position. The total amount of mechanical energy is merely the sum of these two forms of energy. And finally, an object with mechanical energy is able to do work on another object.

With that, we're going to tuck this equation for TME away for a while, and pull it out to use again later this week

2. #040B: How Does Work...Work?

• Let's learn about the relationship between Work & Power: https://ed.ted.com/on/5bau54uF#review
• Read questions 1-9
• Watch the video and answer the questions/solve the problems
• Discuss :-)

At Home Learning (HW)

1. Complete all 9 questions/problems from #040B

If you got stuck, ask a classmate, or contact me via the Remind App

2. #040C: Wednesday we will continue with Power: Watch/take notes/complete edPuzzle on the following:

1. (5:52) Introduction to Power - EDpuzzle

I didn't check Day 39 HW today. If you'd have a deep, burning desire to turn it in, I'll give extra credit for it tomorrow.