Shooting Rubber Bands Overview For this introductory activity you will shoot rubber bands stretched to various distances. Hypothesis: ? Materials: Rubber Band Ruler Data Table Procedures: Write a hypothesis in your composition that states your guess as the the effect that the distance a rubber band is stretched has on the distance the rubber band will fly. Place a rubber band on the edge of the ruler, pull it back to 10 cm, and release the rubber band. Be sure the ruler is parallel to the floor. Measure the distance traveled by the rubber band and record it in a data table. Repeat these steps while increasing the distance the rubber band is pulled back by five centimeters for each release. Average your results and create a line graph of your average data with distance traveled on the y-axis and the distance you pulled the rubber band back on the x-axis. http://www.sciencebuddies.org/science-fair-projects/project_ideas/ApMech_p017.shtml?fave=no&isb=cmlkOjE1MjI3OTc4LHNpZDowLHA6MSxpYTpBcE1lY2g&from=TSW

QOD : 9-29-14 Today, we will do an experiment that tries to answer the question: What variables affect the speed of a pendulum. 1. Spend 5 minutes reading the first page of the handout and write down your guess regarding what affect shortening the length of a pendulum will have on the speed of the pendulum

QOD: 9-29-14 On Friday, we did an experiment that tries to answer the question: What variables affect the speed of a pendulum? We tested how changing the length of the string affected the speed of the pendulum. 1. What did your data show regarding this question? 2. What affect do you think increasing the weight of the pendulum will have on the speed of the pendulum?

QOD 9-29-14 Last Friday we did an experiment to see what variables affect the speed of a pendulum 1. Reread your hypothesis 2. Write a hypothesis that addresses the following question: Does the height from which you drop the pendulum affect the number of swings in 10 seconds?

Data Table Trial 10 cm 15 cm 20 cm 25 cm 30 cm 1 2 3 Average

Questions What patterns or trends did you notice? Was energy used to launch the rubber band? If so, explain your reasoning. What factors could have impacted the accuracy of your data? Did your data support your hypothesis? Explain your reasoning.

Energy Today, we will begin our study of energy. List 3 things that you know about energy List 3 things that you would like to learn about energy or things that you wonder about.

Energy

Energy the ability to do work or cause change measured in units of joules (J) two general types of energy: Potential Kinetic

Work Work is done when an applied force causes an object to move in the direction of the force Units of joules (J) Formula: Work = Force x distance What are some examples of work being done that fit this definition? W = (F)(d) Sample Problem Three students push on a car with 100 N of force and the car moves 10meters.. How much work did the students perform in? = (100N) (10 m) = 1000 N•m or 1000 J Eureka video on work

Work problems: Work=(Force)(Distance) You push a refrigerator with a horizontal force of 100N. If you move the refrigerator a distance of 5meters, how much work do you do? W=Fd F=100N d=5N W=(100N)(5M) You do 500Joules of work

Work problems: How much work do you do when you lift a 100N child 0.5meters? W=Fd F=100N d=0.5meters W=(100N)(0.5meters) You do 50joules of work

QOD 8-1-14 1. How much work do you do if you lift a 9N book 1.7 meters over you head? 2. How many meters over your head do you have to lift a 5N book to do 2.5 J of work?

Potential Energy (PE) stored energy that an object has due to its position or its chemical composition Types of potential energy: Gravitational Potential Energy – results from how high an object is above the earth. Formula: GPE = (mass)(gravity)(height) Elastic Potential Energy – results from stretching or compressing. What is an example of something that stores energy when it stretches or compresses? Chemical Potential Energy- Energy stored in chemical bonds. What is an example of energy stored in a chemical? 0.45 kg Which soccer ball has more gravitational potential energy? Explain your reasoning.

Potential energy question The higher an object is above the earth, the more gravitational potential energy it has. On your white board, draw the path you would take if you were to swing on a playground swing. label the point of highest GPE and the point of lowest GPE.

Which soccer ball has more kinetic energy? Explain your reasoning. Kinetic Energy (KE) energy of motion depends on mass and velocity Formula: KE = ½ (mass)(velocity)2 KE increases as mass or velocity increases and decreases as mass or velocity decreases 2 m/s 3 m/s 0.45 kg Which soccer ball has more kinetic energy? Explain your reasoning.

Kinetic energy question The faster an object moves, the more Kinetic Energy it has. 1. On your white board, draw the path that your swing took yesterday and label the point of highest kinetic energy and the point of the least kinetic energy

Relationship Between PE and KE What is happening to the PE and KE as the soccer ball falls to the feet of the mid-fielder? PE KE What about the PE/KE graph could be considered misleading?

Practice Problems A diver weighing 46 kg is preparing for a dive from the 10 meter diving platform. How much gravitational potential energy does the diver have? A cheetah weighing approximately 50 kg was seen chasing a gazelle at a speed of 32.4 m/s. What is the kinetic energy of the cheetah? PE = mgh Earth’s Gravity P.E. = (46 kg) (9.8 m/s2) (10 m) = 4,508 J KE = 1mv2 2 (1)_____________ 2 (50 kg) (32.4 m/s)2 K.E. = = 26,244 J

Forms of Energy (Grouping Activity) Organize the 24 laminated sheets into six groups. Each group should consist of: words representing a form of energy (bold) some descriptions describing the form of energy (bullet) a visual representation of the form of energy. When you think the sheets are correctly grouped, have me come and confirm whether it is correct. Complete the table.

11/2/15 1) Hand in your vocabulary chart 2) Hand in your Kinetic and Potential energy practice 3) Take out your notebook so we can get reorganized.

Warm up 11/2/15 1. What type of energy is the energy stored in food and gasoline? 2. What type of energy do objects in motion have? 3. List 2 examples of energy that you used today.

Forms of Energy Mechanical Sound Chemical Thermal Electromagnetic Nuclear

Mechanical Energy energy that moves objects the total amount of potential and kinetic energy combined. Example: -A bouncing ball has both KE and PE. Add the 2 together to find mechanical energy http://www.columbiastate.edu/HSS-Textbook-Information

Sound Energy Caused by the vibration of particles in a solid, liquid, or gas must have a medium to travel through - cannot travel through empty space sound in a vacuum This person is listening to someone telling a secret. How are the sound waves being generated?

Chemical Energy potential energy stored in the chemical composition of matter. We eat glucose and convert the chemical energy in the bonds to live. Chemical bonds in gasoline are converted into mechanical energy in our vehicles. The chemical energy in coal is conveted into thermal and electrical energy. C H O HO OH ≈464,000 J ≈347,000 J Glucose

has more thermal energy? Why? when particles move faster they have more thermal energy than when they move slower Which box of particles has more thermal energy? Why?

Electromagnetic Energy Travels through space in the form of electromagnetic waves light, electricity, and magnetism are representative of electromagnetic energy can travel through empty space Image taken from: http://zebu.uoregon.edu/~imamura/122/lecture-2/em.html

Nuclear Energy is released when an atom’s nucleus breaks apart (fission) or when the nuclei of two atoms come together (fusion) Example: Nuclear fission takes place in a nuclear power plant while nuclear fusion takes place in the Sun. + + Is nuclear fission or nuclear fusion taking place? Explain your reasoning. Deuterium Tritium + helium neutron Video on fusion in the sun

Identify the Form of Energy Thermal (burner increases movement of H2O molecules) Mechanical (moving gears) Electromagnetic (radio waves) Chemical (food) Electromagnetic (electricity)

Energy Conversions a change from one form of energy into another during conversions, some energy is usually lost as heat Example Electromagnetic energy (in the form of light) from the Sun is converted, by plants, into chemical energy in the form of glucose 6CO2 + H2O C6H12O6 + 6O2 light energy Light Energy CO2 H2O O2 C6H12O6

Nuclear energy Two types: Fusion occurs when nuclei are smashed together (the sun does this) video Fission occurs when nuclei are split apart. Nuclear bombs and power plants do this.

Identify the Energy Conversions 2. Electromagnetic Energy (electricity moving through the wires) Wires The apparatus to the right was placed into a bell jar. What energy conversions take place when it is operating? Battery Buzzer 1. Chemical energy (in the battery) 3. Sound Energy (noise coming from the buzzer)

In your Notebook Describe all of the energy conversions in the following situation: You turn on a toaster and toast a piece of bread. You lift up and eat the toast. After breakfast, you go for a run.

On your white board On a cold morning you start your car. To melt the ice on the windshield you turn on the heat. Once the ice is clear you drive to school.

On a cold day your rub your hands together to warm them up.

Law of Conservation of Energy states that energy can be neither created nor destroyed the total amount of energy in a closed system is the same energy can be changed from one form to another, but all of the different forms of energy add up to the same total amount of energy PE = 24 J KE = 0 J PE = KE = 12 J 12 J A bird steals a sandwich and drops it from a height of 7 m before eating it. What would be the sandwich’s approximate PE and KE as it falls to the ground if air resistance is negligible? PE = KE = 0 J 24 J

Efficiency = energy output x 100 Energy Efficiency comparison of the amount of energy before a conversion with the amount of useful energy after a conversion the closer the energy (work) output is to the energy (work) input, the more efficient the conversion is more efficient conversions  less waste Formula: Sample Problem A particular cell phone charger uses 4.83 joules per second when plugged into an outlet, but only 1.31 joules per second actually goes into the cell phone battery. The remaining joules are lost as heat. That’s why the battery feels warm after it has been charging for a while. How efficient is the charger? 1.31 J Efficiency = energy output x 100 energy input = ____ x 100 4.83 J = 27.1% Sample Problem taken from: http://www.cposcience.com/home/Portals/2/Media/post_sale_content/PHY2/Ancillaries/SkillSheets/Unit_4/11.1_Efficiency.pdf

Efficiency practice If a child on a swing has 900J of Gravitational potential energy at the top of the swing and 700J of Kinetic energy at the bottom of the swing, what was the efficiency of that conversion? 700J x 100 = 77.7% 900J

How efficient the conversion of electrical energy to thermal energy in your toaster if the input of electricity is 300J and the output of thermal energy is 250J? 250J x 100= 83.3% 300J

Power practice