Physical Science Chapter 5 Energy & Power Bill Nye Energy Video

5.1 The Nature of Energy Energy – the ability to do work or cause a change. Energy – the ability to do work or cause a change. work is the transfer of energy work is the transfer of energy SI unit for energy is the same as the SI unit for work – Joule SI unit for energy is the same as the SI unit for work – Joule Two main types of energy: Kinetic and Potential Two main types of energy: Kinetic and Potential Kinetic Energy: the energy of motion Kinetic Energy: the energy of motion Potential Energy: Energy stored for use at a later time Potential Energy: Energy stored for use at a later time

3 Science STAAR Need to Know Potential (PE) Stored energy

4 Science STAAR Need to Know Kinetic Energy (KE) Energy due to motion of an object Speed & mass affect kinetic energy– Faster/heavier…more Kinetic Energy Did you know that the gas burned in a car engine is chemical energy being turned into Kinetic Energy? Rubber band flying through the air has kinetic energy

5 Science STAAR Need to Know Before the yo-yo begins its fall it has stored energy due to its position. As it falls the potential energy begins to be changed into kinetic energy. At the bottom its potential energy has been converted into kinetic energy 1.A waterfall has both potential and kinetic energy. The water at the top stored potential energy. 2.When the water falls, its potential energy is changed into kinetic energy. At Niagara Falls waters kinetic energy is transformed into mechanical and then electromagnetic energy. Potential Energy

6 Science STAAR Need to Know

Calculating Kinetic Energy Kinetic Energy: the energy of motion Kinetic Energy: the energy of motion The amount of kinetic energy depends on the objects mass and velocity The amount of kinetic energy depends on the objects mass and velocity Energy is transferred during work The more work one does on an object… The more work one does on an object… The more energy one imparts on the object The more energy one imparts on the object Kinetic energy = Mass x Velocity 2 2 When mass is doubled; Kinetic Energy is doubled When velocity is doubled; Kinetic Energy is quadrupled!! KE = ½ mv 2

What’s the Kinetic Energy? What is the Kinetic Energy (in Joules) of an object with a mass of 10 kg and a velocity of 10 m/s? What is the Kinetic Energy (in Joules) of an object with a mass of 10 kg and a velocity of 10 m/s? When mass is doubled; Kinetic Energy is doubled When mass is doubled; Kinetic Energy is doubled When velocity is doubled; Kinetic Energy is quadrupled!! When velocity is doubled; Kinetic Energy is quadrupled!! KE = ½ mv 2

Potential Energy: Energy stored for use at a later time 2 Types: Elastic Potential Energy: Energy stored in springs, bow and arrow, stretched elastic or rubber bands. Associated w/ objects that can be stretched or compressed. Gravitational Potential Energy: Height and weight dependant (notice its weight, NOT mass!) GPE = work done to lift and object to a height GPE = Weight x Height (remember that weight = mass x 9.8 m/s2) GPE = mass x 9.8 m/s2 x Height GPE = 100 N x 300 m = 30,000 Nm = 30,000 Joules

Assignment Read Chapter 13, pages 442 to 446 in text. Compete guided reading handout Due Weds 5/7/2014

Forms of Energy Objectives: Explain how to determine an object’s mechanical energy Identify the form of energy associated with the motion of atoms/molecules in an object Define the 7 forms of Energy

Different Forms of Energy 7 different types : Mechanical Mechanical Radiant (Electromagnetic) Radiant (Electromagnetic) Sound Energy Sound Energy Chemical Energy Chemical Energy Heat (Thermal) Heat (Thermal) Electrical Energy Electrical Energy Nuclear Energy Nuclear Energy

Mechanical Energy Associated w/ the motion (kinetic) and position of an object (potential) Associated w/ the motion (kinetic) and position of an object (potential) Kinetic Energy exists whenever an object which has mass is in motion with some velocity. Everything you see moving about has kinetic energy. Kinetic Energy exists whenever an object which has mass is in motion with some velocity. Everything you see moving about has kinetic energy. Potential Energy exists whenever an object which has mass has a position within a force field. (Gravity, Electric, Magnetic, Elastic) Potential Energy exists whenever an object which has mass has a position within a force field. (Gravity, Electric, Magnetic, Elastic) Mechanical Energy = Potential Energy + Kinetic Energy Mechanical Energy = Potential Energy + Kinetic Energy GPE = Weight x Height

Sound Sound Copyright © 2010 Ryan P. Murphy

Sound Energy: Caused by an object's vibrations. Sound energy is both kinetic and potential energy. Copyright © 2010 Ryan P. Murphy

Activity Simulator: Soundwaves

Thermal Energy The total energy of the particles (atoms and molecules) in an object. The total energy of the particles (atoms and molecules) in an object. As thermal energy increases, the particles increase in speed and the thermal energy (temperature) of the object increases. As thermal energy increases, the particles increase in speed and the thermal energy (temperature) of the object increases.

Chemical Energy the energy stored in chemical bonds. The potential energy stored in compounds. the energy stored in chemical bonds. The potential energy stored in compounds.

Electrical Energy Moving electrical charges. Electricity!! Moving electrical charges. Electricity!!

Electromagnetic energy (Radiant) Travels in waves, associated w/ light, infrared, ultraviolet, microwaves, x-rays, etc Travels in waves, associated w/ light, infrared, ultraviolet, microwaves, x-rays, etc Longer wavelength yields low frequency & low energy Longer wavelength yields low frequency & low energy Shorter wavelength yield high frequency & high energy Shorter wavelength yield high frequency & high energy

Nuclear Energy Associated w/ the fusion or fission of the nucleus. Associated w/ the fusion or fission of the nucleus. The fusion of hydrogen into helium fuels the power of the sun

Energy Transformation & Conservation Objectives: Describe how different forms of energy are related Explain the law of conservation of energy

23 Science STAAR Need to Know Energy Transformations Potential energy A rock sitting at the top of a cliff A rock sitting at the top of a cliff Roller coaster car at the top peak of a hill Roller coaster car at the top peak of a hill A swimmer posed to dive off the end of a diving board A swimmer posed to dive off the end of a diving board NO MOTION !! NO MOTION !! Kinetic energy A bouncing ball A bouncing ball A moving roller coaster A moving roller coaster A track star running A track star running A girl skiing A girl skiing MOTION is the key!!!! MOTION is the key!!!!

Energy Conversions

Energy Conversion and Conservation Most forms of energy can be converted from one type to another. Mechanical Energy = PE + KE Most forms of energy can be converted from one type to another. Mechanical Energy = PE + KE Law of the Conservation of Energy - states that energy cannot be created or destroyed. It simply changes from one form into another Law of the Conservation of Energy - states that energy cannot be created or destroyed. It simply changes from one form into another Einstein’s theory of Relativity - E = mc 2 Einstein’s theory of Relativity - E = mc 2 a small amount of mass can be changed directly into a tremendous amount of energy a small amount of mass can be changed directly into a tremendous amount of energy E = the energy produced E = the energy produced m = the mass being converted m = the mass being converted c = the speed of light (186,000 miles/second) c = the speed of light (186,000 miles/second)

Energy & Power Power: the rate at which work is done Power: the rate at which work is done Power is also rate at which energy is transferred Power is also rate at which energy is transferred Power = work / time and since: Power = work / time and since: Power = Energy Transferred/unit time Power = Energy Transferred Power = Energy Transferred Time Time SI Unit for Power is the Watt SI Unit for Power is the Watt 1 Watt = 1Joule / 1 Second 1 Watt = 1Joule / 1 Second Horsepower : An American unit of power Horsepower : An American unit of power The amount of work a horse does when it lifts The amount of work a horse does when it lifts 33,000 pounds of coal to a height of 1 foot in 1 minute. 33,000 pounds of coal to a height of 1 foot in 1 minute. 1 horsepower = 746 watts 1 horsepower = 746 watts James Watt Same amount of work was done; however there was more power in lifter B since his took less time AB

Power Problems W = F x D P = F x D / T P = 35 N x 10 m / 5 sec P = 350 J / 5 sec = 70 J/sec P = 70 Watts W = P x T convert 1 hour into seconds: 1 hour 60 min x 60 sec 1 hr 1 min Work = 60 watts x 3600 sec = 216,000 Joules = 216 Kilojoules