CHAPTER 15: ENERGY!

RESOURCES Vocabulary Review: Quizlet Ch 15 Doodle Science Playlist: High School Physics

Energy: Measured in joules! The ability to do work Work = Force x distance Measured in joules!

ENERGY

Forms of Energy: Kinetic: energy of movement (depends on mass and velocity)

Forms of Energy: Potential: energy of position - gravitational: depends on mass, height and acceleration due to gravity - elastic: depends on ability to be stretched or compressed - chemical: stored in bonds - electrical: associated with charge - nuclear: stored in the atomic nucleus - electromagnetic: waves (light/rays/sound)

The Law of Conservation of Energy Energy is never created or destroyed – it is transformed from one form to another. (PE+KE)Beginning = (PE+KE)End

The Law of Conservation of Energy Often, kinetic energy will be transformed into thermal energy, via FRICTION. This is the reason we always LOSE efficiency when work is done!

Calculating Kinetic Energy m = mass (kg) v = velocity (m/s) KE = kinetic energy (Joules)

Calculating Kinetic Energy What is the kinetic energy of a 75-kg student running at a speed of 3 m/s?

A. Energy ENERGY ENERGY THERMAL The ability to cause change. internal motion of particles ENERGY MECHANICAL NUCLEAR ENERGY motion of objects changes in the nucleus ELECTRICAL joules (J) CHEMICAL motion of electric charges bonding of atoms

Calculating Potential Energy m = mass (kg) g = acceleration due to gravity (9.8 m/s2) h = height (m) PE = potential energy (Joules)

Calculating Potential Energy A mover carries a television with a mass of 62 kg a distance of 18 m up the stairs. How much potential energy does the TV have? PE = (62)(9.8)(18) = 10,937 J

The Law of Conservation of Energy If 2500-kg roller coaster car begins its descent from 500 m above the first hill, what is its kinetic energy at the bottom of that hill? PE = (2500)(9.8)(500) = 12,250,000 J = KE!

Energy and Work Work & Energy Conservation of Energy Ch. 15 - Energy Energy and Work Work & Energy Conservation of Energy

A. Energy ENERGY ENERGY THERMAL The ability to cause change. internal motion of particles ENERGY MECHANICAL NUCLEAR ENERGY motion of objects changes in the nucleus ELECTRICAL joules (J) CHEMICAL motion of electric charges bonding of atoms

A. Energy Kinetic Energy (KE) Which has the most KE? 80 km/h truck energy in the form of motion depends on mass and velocity 80 km/h 50 km/h Which has the most KE? Which has the least KE? 80 km/h truck 50 km/h motorcycle

A. Energy Potential Energy (PE) stored energy depends on position or configuration of an object Which boulder has greater gravitational PE? What other ways can an object store energy?

W = Fd B. Work W: work (J) F: force (N) d: distance (m) 1 J = 1 N·m transfer of energy through motion force exerted through a distance W = Fd W: work (J) F: force (N) d: distance (m) 1 J = 1 N·m Distance must be in direction of force!

B. Work Brett’s backpack weighs 30 N. How much work is done on the backpack when he lifts it 1.5 m from the floor to his back? GIVEN: F = 30 N d = 1.5 m W = ? WORK: W = F·d W = (30 N)(1.5 m) W = 45 J F W d

B. Work d W F GIVEN: m = 40 kg d = 1.4 m - during d = 2.2 m - after A dancer lifts a 40 kg ballerina 1.4 m in the air and walks forward 2.2 m. How much work is done on the ballerina during and after the lift? GIVEN: m = 40 kg d = 1.4 m - during d = 2.2 m - after W = ? WORK: W = F·d F = m·a F =(40kg)(9.8m/s2)=392 N W = (392 N)(1.4 m) W = 549 J during lift No work after lift. “d” is not in the direction of the force. F W d

C. Conservation of Energy Law of Conservation of Energy Energy may change forms, but it cannot be created or destroyed under ordinary conditions. EX: ENERGY CONVERSIONS PE  KE mechanical  thermal chemical  thermal

C. Conservation of Energy PE  KE View pendulum animation. View roller coaster animation.

C. Conservation of Energy Mechanical  Thermal View rolling ball animations. View skier animation.

Energy and MASS E=mc2 E: energy (J) M: mass (kg) C: speed of light (3.0X 108 m/s) Einstein showed that mass and energy are equivalent and can be converted into each other.

Energy and MASS E=mc2 E: energy (J) M: mass (kg) C: speed of light (3.0X 108 m/s) How much energy is released if 1 gram of matter is completely converted into energy?

Energy Resources History of Human Energy Use: CC 7 min. Non-renewable Energy Resources: Doodle Renewable Energy Resources: Doodle 1 & Doodle 2 Energy  National Grid

Writing/Drawing Assignment YOUR TURN TO DOODLE  Writing/Drawing Assignment On a piece of paper draw & LABEL: A building with a purpose of your choice (i.e. gym/school/house, etc.) Must use 4 types of Energy Resources Strive for a sustainable design. Write a paragraph about your building: What is its purpose? How does the design conserve energy? What energy resources does it use? Is this practical? Could you market this design? Why or Why not?

HEAT – Thermal Energy Transfer Ch. 16.1 & 16.2 -- Thermodynamics Kinetic Theory – energy determines state of matter What is heat? Transfer of thermal energy from one object to another Heat Transfer - Conduction & Convection Radiation What is temperature? Measure of heat compared to a reference point (degrees)

Kinetic Energy Practice Problems   What is the Kinetic Energy of a 150 kg object that is moving with a speed of 15 m/s? An object has a kinetic energy of 25 J and a mass of 34 kg , how fast is the object moving? An object moving with a speed of 35 m/s and has a kinetic energy of 1500 J, what is the mass of the object. What is the Kinetic Energy of a 1200 kg object that is moving with a speed of 24 m/s? An object has a kinetic energy of 14 J and a mass of 17 kg , how fast is the object moving? An object moving with a speed of 67 m/s and has a kinetic energy of 500 J, what is the mass of the object. What is the Kinetic Energy of a 478 kg object that is moving with a speed of 15 m/s? An object has a kinetic energy of 88 J and a mass of 45 kg , how fast is the object moving? An object moving with a speed of 21 m/s and has a kinetic energy of 140 J, what is the mass of the object. What is the Kinetic Energy of a 100 kg object that is moving with a speed of 12.5 m/s?

An object has a kinetic energy of 14 J and a mass of 17 kg , how fast is the object moving?