Aim: What are the different kinds of energy? Do Now: Take a minute to write down on a piece of paper if you going to take the regent’s exam or not. Include your name and section number. Put the tally in the box. You may change your answer later. Homework: Choose a topic from the list to write about Due 2/4 Finish the worksheet due 2/13/15 New Project is due Feb 22 nd How do we know something has energy and in what ways do we witness the effect of something having energy?

Agenda Do Now – 2 min – Regent's Tally Mini Lesson – 25 min – What is Energy and what are its forms Activity – 10 min – what are some of the energy types you know? determine the different types of energy? Wrap up – 8 min – Exit slip Review – 10 min – Old concepts review

Working definitions Energy: the capacity to do work. Joule: The unit for work and energy 1 J = 1 Nm = 1 kgm 2 /s 2 Video :

Two main categories of energy – Kinetic Energy: Energy of motion A moving baseball can do work A falling anvil can do work – Potential Energy: Stored (latent) capacity to do work Gravitational potential energy (perched on cliff) Mechanical potential energy (like in compressed spring) Chemical potential energy (stored in bonds) Nuclear potential energy (in nuclear bonds)

Kinetic Energy The kinetic energy for a mass in motion is K.E. = ½mv 2 Example: 1 kg at 10 m/s has 50 J of kinetic energy

KE continue… Kinetic energy is proportional to v 2 … Watch out for fast things! – Damage to car in collision is proportional to v 2 – Trauma to head from falling anvil is proportional to v 2, or to mgh (how high it started from) – Hurricane with 120 m.p.h. packs four times the punch of gale with 60 m.p.h. winds

Aim: what is a closed system? Do Now: Write down a scenario explaining where there is energy and what kind. An example: A boy walks up a flight of stairs (uses chemical energy converting it into mechanical energy which is converted into potential energy at the top.) and then drops a penny from the window (gravitational potential energy is converted into kinetic energy as the penny falls). Homework: Choose a topic from the list to write about Due 2/4 Finish the worksheet due 2/13/15 New Project is due Feb 22 nd How do we know something has energy and in what ways do we witness the effect of something having energy?

Gravitational Potential Energy PE = mgh m = mass of the object g = acceleration due to gravity h = height the object is at. The higher the object is the more potential it has.

Example Ball dropped from rest at a height h (P.E. = mgh) hits the ground with speed v. Expect ½mv 2 = mgh – h = ½gt 2 – v = gt  v 2 = g 2 t 2 – mgh = mg  (½gt 2 ) = ½mg 2 t 2 = ½mv 2 sure enough – Ball has converted its available gravitational potential energy into kinetic energy: the energy of motion

Energy Conversion Energy can be converted between types Energy can’t be created or destroyed Doing work on something changes that object’s energy by amount of work done, transferring energy from the agent doing the work

Energy Conservation The total energy (in all forms) in a “closed” system remains constant This is one of nature’s “conservation laws” – Conservation applies to: Energy (includes mass via E = mc 2 ) Momentum Angular Momentum Electric Charge

Total energy of a closed system KE initial + PE initial = KE final + PE final ½ mv 2 + mgh = ½ mv 2 + mgh

Total energy in non ideal systems KE initial + PE initial = KE final + PE final + E lost ½ mv 2 + mgh = ½ mv 2 + mgh + Heat

Work defined Work carries a specific meaning in physics – Simple form: work = force  distance W = F · d

Work explained Work can be done by you, as well as on you – Are you the pusher or the pushee Work is a measure of expended energy – Work makes you tired Machines make work easy (ramps, levers, etc.) – Apply less force over larger distance for same work

Aim: How do we find the energy stored in a spring? Do Now: 1. Write down the topic you chose from the list and the date to present on it. 2. What is the energy in a 5.0 kg cat on the third floor (9.0 m above the ground) How fast will the cat be traveling before landing on the ground? [ignore air resistance] Homework: Finish the worksheets due 2/13/15 the first article is Due 2/20 read about it by the 23 New Project is due Feb 22 nd How do we know something has energy and in what ways do we witness the effect of something having energy?

What is the energy in a 5.0 kg cat on the third floor (9.0m above the ground) How fast will the cat be traveling before landing on the ground? [ignore air resistance] G: m = 5.0kg, h = 9.0m, g= 9.8m/s 2 U: PE =?, v=? E: PE = mgh KE = ½ mv 2 PEi+ KEi = PEf +KEf PEi = KEf mgh = ½ mv 2 S:(5kg)(9.8m/s 2 )(9m) = ½ (5kg) v 2 S: 441J = 2.5kg v m 2 /s 2 = v m/s = v = 13m/s

Spring Equilibrium The equilibrium position is the position that the spring naturally assumes when there is no force applied to it. If a spring is not stretched or compressed, then there is no elastic potential energy stored in it. The spring is said to be at its equilibrium position.

Hook’s law F spring = k x The force stored in a spring is equal to how elastic it is (k) times the distance it is compressed or expanded (x). Every spring has a different constant!!

Elastic Potential Energy PE spring = 0.5 k x 2 k = spring constant x = the distance the spring is compressed or expanded. The energy stored in a spring or elastic when it is removed from equilibrium.

Activity Find the spring constant and potential energy in your spring scale!

What is Power? Power is simply energy exchanged per unit time, or how fast you get work done (Watts = Joules/sec) One horsepower = 745 W

Power examples Perform 100 J of work in 1 s, and call it 100 W Run upstairs, raising your 70 kg (700 N) mass 3 m (2,100 J) in 3 seconds  700 W output! Shuttle puts out a few GW (gigawatts, or 10 9 W) of power!

Do Now cat is back! G: m = 5.0kg, h = 9.0m, g= 9.8m/s 2, t= 0.7s Found: v = 13m/s, PE = 441 J U: Fg= ?, W=?, P=? E: Fg = mg, S: Fg = (5kg)(9.8m/s 2 ) S:Fg = 49N

Do Now cat is back! G: m = 5.0kg, h = 9.0m, g= 9.8m/s 2, t= 0.7s Found: v = 13m/s, PE = 441 J. Fg= 49N U: Fg= ?, W=?, P=? E: W=fd S: W = (49N)(9m) S:W = 441J

Do Now cat is back! G: m = 5.0kg, h = 9.0m, g= 9.8m/s 2, t= 0.7s Found: v = 13m/s, PE = 441 J. Fg= 49N, W = 441J U: Fg= ?, W=?, P=? E: P=W/t S: P = (441J)/(0.7s) S:p = 630Watt

Wow Curls !! Ms. Adam’s Curly Cues have a mass of 25g each. As she pulls on one with a force of 0.02N it expands a distance of 7 cm. What is the spring constant for the curl Ms. Adam pulled? How much energy is stored in her curl before it was released? How fast did was her curl traveling back to equilibrium? How much work was done by the curl? If it took 0.5 sec for it to go back what is the power of her curl?

Momentum Often misused word, though most have the right idea Momentum, denoted p, is mass times velocity p = m·v Momentum is a conserved quantity (and a vector) – Often relevant in collisions (watch out for linebackers!)

1. Two pieces of flint rock produce a visible spark when they are struck together. During this process, mechanical energy is converted into (1) nuclear energy and electromagnetic energy (2) internal energy and nuclear energy (3) electromagnetic energy and internal energy (4) elastic potential energy and nuclear energy

2. What is the total energy released when 9.11 × 10 −31 kilogram of mass is converted into energy? (1) 2.73 × 10 −22 J (3) 9.11 × 10 −31 J (2) 8.20 × 10 −14 J (4) 1.01 × 10 −47 J E = mc 2 c= speed of light in a vacuum = 3.00x10 8 m/s E = (9.11x kg)(3.00x10 8 m/s) 2 = 81.99x E= 8.20 x kgm 2 /s 2

3. A shopping cart slows as it moves along a level floor. Which statement describes the energies of the cart? (1) The kinetic energy increases and the gravitational potential energy remains the same. (2) The kinetic energy increases and the gravitational potential energy decreases. (3) The kinetic energy decreases and the gravitational potential energy remains the same. (4) The kinetic energy decreases and the gravitational potential energy increases.

4. A 25-gram paper cup falls from rest off the edge of a tabletop 0.90 meter above the floor. If the cup has 0.20 joule of kinetic energy when it hits the floor, what is the total amount of energy converted into internal (thermal) energy during the cup’s fall? (1) 0.02 J (3) 2.2 J (2) 0.22 J (4) 220 J

5. Regardless of the method used to generate electrical energy, the amount of energy provided by the source is always greater than the amount of electrical energy produced. Explain why there is a difference between the amount of energy provided by the source and the amount of electrical energy produced. [1]

6. When a teacher shines light on a photocell attached to a fan, the blades of the fan turn. The brighter the light shone on the photocell, the faster the blades turn. Which energy conversion is illustrated by this demonstration? (1) light → thermal → mechanical (2) light → nuclear → thermal (3) light → electrical → mechanical (4) light → mechanical → chemical

(1)decreases, then increases (2) increases, only (3) increases, then decreases (4) remains the same 7. In the diagram below, an ideal pendulum released from position A swings freely to position B. As the pendulum swings from A to B, its total mechanical energy

8. Which graph represents the relationship between the kinetic energy and the speed of a freely falling object?

Base your answers to questions 9 to 12 on the following: A 30.4-newton force is used to slide a 40.0-newton crate a distance of 6.00 meters at constant speed along an incline to a vertical height of 3.00 meters 9. Determine the total work done by the 30.4-newton force in sliding the crate along the incline. [1] G: F = 30.4N, Fg = 40.0 N, d= 6m, h=3 m U: work =?? E: W = Fd S: W = (30.4N)(6m) S: W = J

A 30.4-newton force is used to slide a 40.0-newton crate a distance of 6.00 meters at constant speed along an incline to a vertical height of 3.00 meters 10. Calculate the total increase in the gravitational potential energy of the crate after it has slid 6.00 meters along the incline. [Show all work, including the equation and substitution with units.] [2] G: F = 30.4N, Fg = 40.0 N, d= 6m, h=3 m U: PE =?? E: PE = mgh S: PE = (40N)(3m) S: PE = 120 J at the top 0 J at the bottom

A 30.4-newton force is used to slide a 40.0-newton crate a distance of 6.00 meters at constant speed along an incline to a vertical height of 3.00 meters 11. State what happens to the kinetic energy of the crate as it slides along the incline. [1] G: F = 30.4N, Fg = 40.0 N, d= 6m, h=3 m U: KE =?? As the crate slide down the incline its kinetic energy increases.

A 30.4-newton force is used to slide a 40.0-newton crate a distance of 6.00 meters at constant speed along an incline to a vertical height of 3.00 meters 12. State what happens to the internal energy of the crate as it slides along the incline. G: F = 30.4N, Fg = 40.0 N, d= 6m, h=3 m U: Internal energy The internal energy of the crate increase as it slides along the incline.