HON PHYSICS DAY 35 It is time for topic 6 1) We start our 6th topic of Physics: Energy and Work! 2) You start by making a list… 3) You get a great flowchart from me, and we discuss two forms of energy and work 4) We learn a lot about work and energy and apply it 5) We discuss the idea of total energy of the system, and see a kickbutt roller coaster

Next Week… Wednesday Dec 17th/Thursday Dec 18th Our 2nd examination Your topics: Momentum and Impulse, and the energy stuff we get through this week.

Now for something kind of New. Your task: Come up with as many energy forms as you can in 5 minutes. Get ready to defend/explain/shout from your list.

TOPIC 5: ENERGY AND WORK Work: Ability to apply a force over a distance, and is the change in an energy form A force opposite of motion is a negative work. A force in the same direction of motion is positive work Energy: Ability to do work, is in many forms In an isolated system, the amount of energy in the system does not change.

The Forms We care about Kinetic and Potential. Kinetic: Energy of motion. Potential: Energy stored in a ‘field’. For us, usually in the form of Gravity.

Problems For You… I suggest cutting out and taping it in Lets do this

As going up the hill, the SYSTEM energy is changing from:________________________

D A) There is a change in K and PE here. We can use the change of each to find Work. But we don’t know the initial velocity, so we can only use the change of PE. W = ΔPE = mghf –mgh0

How fast is what form of energy How fast is what form of energy?.... And at R, what form/forms does that energy take?

W = 500,000J = ΔK = Kf – Ki = ½ (m)(v2) – ½ m (02) B B) At R, the height is zero. So in this isolated system, the work going up = work going down. So we can use that work (and the fact that the velocity at Q is zero) to get the final K. W = 500,000J = ΔK = Kf – Ki = ½ (m)(v2) – ½ m (02)

Lets See and Draw a Roller Coaster This is the TOP THRILL DRAGSTER. Height of the coaster: 420 feet tall (130m) Accelerated to a speed of 120 mph (190 km/h) in 3.8 seconds and then begins to vertically climb. 17 seconds for the ride 18 riders per train, train mass is 15 tons (13,600kg) empty. Lets see it!

5 dots correspond to different parts of the ride. Dark Blue: At the start. Moving very fast. No height. So 100% of the system energy is Kinetic.

5 dots correspond to different parts of the ride. Red: Halfway up. If there was no energy ‘dissipated’ (isolated system!) 50% of system energy is Kinetic, 50% is Potential

5 dots correspond to different parts of the ride. Green: At the top. Not moving. So 100% of the system energy is Potential (if isolated)

5 dots correspond to different parts of the ride. Light Blue: Halfway down. If there was no energy ‘dissipated’ (isolated system!) 50% of system energy is Kinetic, 50% is Potential

5 dots correspond to different parts of the ride. Pink: At bottom. 100% of system energy is Kinetic (if isolated). Then to stop it the coaster absorbs all the energy, making it stop. This is an outside force.

So Lets DO A Bar Graph Lets compare the bottom and top

So Lets DO A Bar Graph Lets compare the bottom and halfway up.

BUT WHAT IF IT WAS NOT ISOLATED? What would happen?

So Lets DO A Bar Graph Lets compare the bottom and top.