1. Chapter 4

2. The nature of energy Energy: The ability to do work or cause change All energy involves either motion or position Where are we using energy right now?

3. What are some types of energy? Thermal energy : The total kinetic energy of particles that make up an object Chemical energy: The energy of a compound changes as the atoms are rearranged to form new compounds. Electrical energy: the energy of moving electrons Sound energy: The energy of vibration Light energy: The energy of vibration of electrically charged particles Nuclear energy: the energy associated with changes in the nucleus of an atom

4. Mechanical NRG Mechanical energy is the total amount of potential and kinetic energy in a system

5. Kinetic energy Kinetic energy is energy in the form of motion.

6. Potential energy is stored energy because of position or shape

7. Energy transfer

8. How to calculate kinetic energy: Kinetic energy = ½ (mass x velocity 2 ) or KE = ½ (mv 2 ) Labeled as Joules Joule is expressed in N x m or 1 Joule= 1 kg * (m/s)2 What is the kinetic energy of a 45 kg object moving at 13 m/sec? mass = 45 kg velocity = 13 m/sec KE = ½ (mv2) So… KE = 1/2 (45 kg)(13 m/sec)2 Solving the equation gives a kinetic energy value of 3802.5 J

9. Calculate Determine the kinetic energy of a 1000-kg roller coaster car that is moving with a speed of 20.0 m/s. KE = (0.5) * (1000 kg) * (20 m/s)2 KE = 200 000 Joules If the roller coaster car in the above problem were moving with twice the speed, then what would be its new kinetic energy? KE = 0.5*1000 kg*(40 m/s)2 KE = 800 000 Joules As your speed doubles your kinetic energy quadruples.

10. Gravitational Potential Energy Grav. Potential energy = weight x height Or….. PE = w x h Elastic Potential energy: energy stored by compressing or stretching something A 37 N object is lifted to a height of 3 meters. What is the potential energy of this object? weight = 37 N height = 3 meters Solving the problem gives a potential energy value of 111 J.