Ch. 13 Work and Energy

Warm Up ( ) Explain what work and energy mean in terms of science.

Outline Objectives Bouncing Ball Work and energy 13.1 Read How do you work?

Objectives Students will be able to explain what happens to a bouncing basketball in terms of work and energy Students will be able to calculate work being done on a notebook during the lab Students will be able to identify the difference between work and energy Students will be able to explain how to calculate work.

Bouncing Ball Drop a large ball on a hard, flat floor. Let it bounce several times. Notice the height the ball reaches after each bounce Observe and Think: – How did the height change? – Why do you think this happens? – Sketch the patch of the ball through several bounces

How do you work? P. 419 Procedure – Lift a book from the floor to your desktop. Try to move the book at a constant speed – Now lift the book again, but stop about halfway up and hold the book still for about 30 seconds. Then continue lifting the book to the desktop. What do you think? – Do you think you did more work the first time you lifted the book or the second time you lifted the book? – What do you think work means?

13.1 Work is the use of force to move an object Force is necessary to do work – Work: the use of force to move an object some distance Work is done only when you exert a force on an object and move it Work done by a force is related to the size of the force and the distance over which the force is applied Work = Force * distance W = Fd Joule – standard unit to measure work (J) it is the product of distance and force or (N*m)

13.1 Work is the use of force to move an object Objects that are moving can do work – Objects in motion do work as well – Water wheel

How much work does it take? P. 422 Procedure – Have a partner help you measure how high your shoulders are from the ground. Record the distance in meters. Round to the nearest tenth of a meter – Attach the notebook to the spring scale. Then slowly lift the notebook to your shoulder and see how much force your are exerting. Record the amount in Newtons – Calculate the work you did while lifting one notebook. Use this information to estimate how much work you do every day when you pick up all of your notebooks to take them to school

How much work does it take? What do you think – Approximately how much work does it take to pick up your notebook? – How would the amount of work you do change if you were shorter? Taller? – How much would are you doing on the notebook if you have stopped to talk to a friend? Challenge – If you pick up a notebook 10 times a day during the school year, how much work do you do on the notebook in one year? (Assume there are 180 school days in a year)

Warm Up ( ) What is kinetic energy? What is potential energy? How are these two terms related, and how are they different?

Outline Objectives How much work does it take?

Objectives Students will be able to explain what happens to a bouncing basketball in terms of work and energy Students will be able to calculate work being done on a notebook during the lab Students will be able to identify the difference between work and energy Students will be able to explain how to calculate work.

How much work does it take? P. 422 Procedure – Have a partner help you measure how high your shoulders are from the ground. Record the distance in meters. Round to the nearest tenth of a meter – Attach the notebook to the spring scale. Then slowly lift the notebook to your shoulder and see how much force your are exerting. Record the amount in newtons – Calculate the work you did while lifting one notebook. Use this information to estimate how much work you do every day when you pick up all of your notebooks to take them to school

How much work does it take? What do you think – Approximately how much work does it take to pick up your notebook? – How would the amount of work you do change if you were shorter? Taller? – How much work are you doing on the notebook if you have stopped to talk to a friend? Challenge – If you pick up a notebook 10 times a day during the school year, how much work do you do on the notebook in one year? (Assume there are 180 school days in a year)

13.2 Energy is transferred when work is done Work transfers energy – Energy is the ability of a person or an object to do work or to cause a change Work changes potential and kinetic energy – Kinetic energy: energy of motion – Potential energy: stored energy, energy an object has due to its position or its shape

13.2 Energy is transferred when work is done Gravitational Potential Energy = mass * gravitational acceleration* height GPE = mgh page 427 – work through the example together Kinetic Energy = (mass * sq. velocity) / 2 P. 428 – work through the example together

13.2 Energy is transferred when work is done Mechanical Energy – the energy possessed by an object due to its motion or position – Combined potential and kinetic energy – ME = PE + KE

13.2 Energy is transferred when work is done Total amount of energy is constant – Law of conservation of energy: energy can be transferred and transformed, but all of the energy is still present somewhere in one form or another – Losing mechanical energy – read through the section on page 430 to understand how a pendulum works and eventually stops Forms of energy – Thermal, chemical, nuclear, electromagnetic

How does mechanical energy change? P. 429 Procedure: 1.Find and record the mass of the ball 2.Build a ramp with the board and books. Measure and record the height of the ramp. You will place the ball at the top of the ramp, so calculate the ball’s potential energy at the top of the ramp using mass and height. 3.Mark a line on the floor with tape 30 cm from the bottom of the ramp 4.Place the ball at the top of the ramp and release it without pushing. Time how long the ball takes to travel from the end of the ramp to the tape 5.Calculate the ball’s speed using the time you measured in step 4. use this speed to calculate the ball’s kinetic energy after it rolled down the ramp

How does mechanical energy change? What do you think? – At the top of the ramp, how much potential energy did the ball have? How much kinetic energy did the ball have at the top of the ramp? What was the mechanical energy of the ball at the top of the ramp? – Compare the ball’s mechanical energy at the top of the ramp with its mechanical energy at the bottom of the ramp. Are they the same? Why or why not? Challenge – Other than gravity, what forces could have affected the movement of the ball?

Warm Up (5-1-15) How are kinetic energy and potential energy related to an object’s position?

Outline Objectives How does mechanical energy change?

Objectives Students will construct ramps to conduct experiments Students will measure kinetic energy and potential energy to calculate mechanical energy Students will determine the difference in energy from the beginning and end of experiments Students will explain how potential energy relates to position of objects.

Work, Energy, and Power - Hockey 2e39-49a df89eb/work-energy- power 2e39-49a df89eb/work-energy- power Golf learn/ # learn/ #

How does mechanical energy change? P. 429 Procedure: 1.Find and record the mass of the ball 2.Build a ramp with the board and books. Measure and record the height of the ramp. You will place the ball at the top of the ramp, so calculate the ball’s potential energy at the top of the ramp using mass and height. 3.Mark a line on the floor with tape 30 cm from the bottom of the ramp 4.Place the ball at the top of the ramp and release it without pushing. Time how long the ball takes to travel from the end of the ramp to the tape 5.Calculate the ball’s speed using the time you measured in step 4. use this speed to calculate the ball’s kinetic energy after it rolled down the ramp

How does mechanical energy change? What do you think? – At the top of the ramp, how much potential energy did the ball have? How much kinetic energy did the ball have at the top of the ramp? What was the mechanical energy of the ball at the top of the ramp? – Compare the ball’s mechanical energy at the top of the ramp with its mechanical energy at the bottom of the ramp. Are they the same? Why or why not? Challenge – Other than gravity, what forces could have affected the movement of the ball?

13.3 Power is the rate at which work is done Power can be calculated from work and time – Power: the rate at which you do work Power = work / time P = W/t Watt (W) standard unit for power, joules of work per second – P. 436 example problem – Horsepower – amount of work a horse can do in a minute

How much power do you have? P. 437 Procedure – Measure a length of 5 meters on the floor. Mark the beginning and the end of the 5 meters with tape. – Attach the object to the spring scale with a piece of string. Slowly pull the object across the floor using a steady amount of force. Record the force and the time it takes you to pull the object

How much power do you have? What do you think? – How much power did you use to pull the object 5 meters? – How do you think you could increase the power you used? How could you decrease the power? Challenge – How quickly would you have to drag the object along the floor to produce 40 watts of power?

Warm Up (5-4-15) Explain how energy can be transferred between kinetic energy and potential energy.

Outline Objectives How much Power do you have?

Objectives Students will construct ramps to conduct experiments Students will measure kinetic energy and potential energy to calculate mechanical energy Students will determine the difference in energy from the beginning and end of experiments Students will explain how potential energy relates to position of objects.

How much power do you have? P. 437 Procedure – Measure a length of 5 meters on the floor. Mark the beginning and the end of the 5 meters with tape. – Attach the object to the spring scale with a piece of string. Slowly pull the object across the floor using a steady amount of force. Record the force and the time it takes you to pull the object

How much power do you have? What do you think? – How much power did you use to pull the object 5 meters? – How do you think you could increase the power you used? How could you decrease the power? Challenge – How quickly would you have to drag the object along the floor to produce 40 watts of power?

Warm Up (5-5-15) Explain how a pendulum works in terms of energy.

Outline Objectives How much power do you have?

Objectives Students will construct ramps to conduct experiments Students will measure kinetic energy and potential energy to calculate mechanical energy Students will determine the difference in energy from the beginning and end of experiments Students will explain how potential energy relates to position of objects.

How much power do you have? P. 437 Procedure – Measure a length of 5 meters on the floor. Mark the beginning and the end of the 5 meters with tape. – Attach the object to the spring scale with a piece of string. Slowly pull the object across the floor using a steady amount of force. Record the force and the time it takes you to pull the object

How much power do you have? What do you think? – How much power did you use to pull the object 5 meters? – How do you think you could increase the power you used? How could you decrease the power? Challenge – How quickly would you have to drag the object along the floor to produce 40 watts of power?

Warm Up (5-6-15) Explain what horsepower is and where you have heard this term before.

Outline Objectives Read 13.2 and 13.3 Notes 13.2 and 13.3

Objectives Students will be able to explain what power is Students will be able to calculate power for given equations. Students will be able to explain what horsepower is and what the origin of horsepower is.

13.3 Power is the rate at which work is done Power can be calculated from work and time – Power: the rate at which you do work Power = work / time P = W/t Watt (W) standard unit for power, joules of work per second – P. 436 example problem – Horsepower – amount of work a horse can do in a minute

Phone Book Friction HIBo HIBo

Warm Up (5-7-15) Write down the equation to calculate Power. Now use that formula to solve the following problem… – A light bulb used 600 J of energy in 6 s. What is the power of the light bulb.

Outline Objectives Mythbusters – the physics behind it

Objectives Students will be able to explain what power is Students will be able to calculate power for given equations. Students will be able to explain what horsepower is and what the origin of horsepower is.

The Physics of See Saws shows/mythbusters/about-this-show/physics- of-seesaws/ shows/mythbusters/about-this-show/physics- of-seesaws/

Warm Up (5-8-15) Give 4 examples of power usage in your everyday life. Pick one of those examples and develop a sample problem to solve for power.

Outline Objectives Lab quest day!

Objectives Students will be able to better explain how to handle the labquest technology and how to create graphs using that technology

Warm Up ( ) Write down anything that you are still confused about chapter 11,12 and 13. Think about forces, newton’s laws of motion, power, energy, and work.

Outline Objectives Review for Final

Objectives Students will be able to better explain how to handle the labquest technology and how to create graphs using that technology Students will be reviewing for their final exam by playing jeopardy

Jeopardy!

Warm Up ( ) Write down everything you can remember about chapter 11,12 and 13. Think about forces, newton’s laws of motion, power, energy, and work.

Outline Objectives Final exam

Objectives Students will demonstrate knowledge of power, energy, work, and forces by completing the final exam.

Warm Up ( ) What are some general science questions that you have and would like to be answered?

Outline Objectives Final exam

Objectives Students will demonstrate knowledge of power, energy, work, and forces by completing the final exam.

Warm Up ( ) Write down one thing that you thought you did really well during this semester that helped you take responsibility for your own grade.

Outline Objectives Final exam

Objectives Students will demonstrate knowledge of power, energy, work, and forces by completing the final exam.

Warm Up ( ) Write down one thing that was difficult about the past semester but that still helped you learn.

Outline Objectives Final exam

Objectives Students will demonstrate knowledge of power, energy, work, and forces by completing the final exam.