Transcript Energy
ENERGY ENERGY The ability to do work. Many forms Unit of measure: joule (J) Amount of force of one newton over one meter. 1J = KINETIC ENERGY The energy of an object in motion Kinetic energy of an object depends on its mass and speed. Kinetic Energy = ½mv2 If you double the mass of an object, you double the KE If you double the speed of an object, you quadruple the KE YOU SERVE A VOLLEYBALL WITH A MASS OF 2.1 KG. THE BALL LEAVES YOUR HAND WITH A SPEED OF 30 M/S. WHAT IS THE KINETIC ENERGY OF THE VOLLEYBALL? KE = ½mv2 KE = ½ * 2.1kg * (30m/s)2 KE = ½ * 2.1kg * 900m2/s2 KE = ½ * 1890kg*m2/s2 KE = 945J KE = 900J NOW, TRY ONE FOR YOURSELF! A 50-KILOGRAM BOY AND HIS 100-KILOGRAM FATHER WENT JOGGING. BOTH RAN AT A RATE OF 5 M/SEC. WHO HAD MORE KINETIC ENERGY? KE = ½mv2 KE(boy) = ½ * 50kg * (5m/s)2 2 2 KE(boy) = ½ * 50kg * 25m /s 2 2 KE(boy) = ½ * 1250kg*m /s KE(boy) = 625J = 600J KE(father) = ½ * 100kg * (5m/s)2 2 2 KE(father) = ½ * 100kg * 25m /s 2 2 KE(father) = ½ * 2500kg*m /s KE(father) = 1250J = 1000J POTENTIAL ENERGY Stored energy that is a result of position or shape. GRAVITATIONAL POTENTIAL ENERGY The potential energy that is the result of an object’s height. The higher an object, the greater the PE PE = mgh m = mass h = height g = acceleration due to gravity 9.8m/s2 WHAT IS THE POTENTIAL ENERGY OF A 15.0KG CINDER BLOCK SITTING ON A PLATFORM 10.0M HIGH? PE = mgh PE = 15.0kg * 9.80m/s2 * 10.0m PE = 1470 kg * m2/s2 PE = 1470 J GUESS WHAT’S NEXT? That’s right….try one on your own! WHAT IS THE POTENTIAL ENERGY OF A 80.0KG DIVER STANDING ON A PLATFORM 10.0M ABOVE A POOL? PE = mgh PE = 80.0kg * 9.80m/s2 * 10.0m PE = 7840kg * m2/s2 PE = 7840J ELASTIC POTENTIAL ENERGY The potential energy of an object that is stretched or compressed. OTHER FORMS OF ENERGY MECHANICAL ENERGY The energy associated with the motion and position of everyday objects The sum of an object’s potential and kinetic energy. THERMAL ENERGY The total kinetic and potential energy contained in the atoms of an object. The faster the atoms in an object move, the greater its thermal energy. CHEMICAL ENERGY The energy stored in the chemical bonds of a substance. Hydrocarbons Exothermic reactions ELECTRICAL ENERGY The energy associated with electrical charges. Work performed by the transfer of electrons from one atom to another. ELECTROMAGNETIC ENERGY Energy that travels in waves. Visible light X-rays NUCLEAR ENERGY Energy stored in the nucleus of an atom Large amounts of potential energy Fission The energy released when the nucleus of an atom is split apart. Fusion The energy released when two small nuclei fuse together to make one large nucleus. ENERGY CONVERSION Energy can be converted from one form to another Digestion of food Nuclear power plant Chemical energy → mechanical energy Nuclear energy → Electrical energy Light bulb Electrical energy → Electromechanical energy WITH YOUR PARTNER, BRAINSTORM AS MANY WAYS IN WHICH ENERGY IS CONVERTED FROM ONE FORM TO ANOTHER AS YOU CAN THINK OF. LAW OF CONSERVATION OF ENERGY Energy cannot be created or destroyed. ENERGY AND MASS Albert Einstein E = mc2 Where c=speed of light, 3.0x108m/s If 1 gram of matter were converted entirely to energy: E = 1x10-3kg x 3.0x108 x 3.0x108 = 9x1013J