11.30 and 12.3

1. 11.30 and 12.3

2. Warm-up #2 12/3/12 In a paragraph… Explain how work can be done to cause energy transformation. Give an example. (Hint: think back to the Rube Goldberg cartoons.)

3. How does work increase potential energy? • When you wind-up a wind-up toy, the energy is stored in its spring. • Elastic potential energy is stored when something “stretchy” or “springy” is stretched or compressed.

4. Conservation of Mechanical Energy • Mechanical energy is the sum of kinetic energy, gravitational potential kinetic energy, and elastic potential energy in a system. • A system is a collection of objects that interact. • Conservation of mechanical energy: If there is no friction or air resistance, the mechanical energy of a system changes only if the system does work on something else or energy is added from an outside source.

5. Conservation of Mechanical Energy • Kinetic Energy = Potential Energy in steps 2& 4. • Kinetic Energy is at its maximum in steps 1 & 5. • Potential energy is at its maximum in step 3. 3 2 4 1 5

6. How does work affect kinetic energy? • A moving object has the capacity to do work due to its kinetic energy. • The factors that control the amount of work a moving object can do are the same as the factors that control the kinetic energy the object has: mass and speed. • To stop the marbles, the cups did negative work on the marbles to bring the kinetic energy to zero. • Potential energy can also do work.

7. How does work increase potential energy? • When you wind-up a wind-up toy, the energy is stored in its _______________. • Elastic potential energy is stored when something “stretchy” or “springy” is _____________ or _______________.

8. Conservation of Mechanical Energy • ______________________ is the sum of kinetic energy, gravitational potential kinetic energy, and elastic potential energy in a system. • A system is a collection of ____________ that __________________. • _____________________ of mechanical energy: If there is no friction or air resistance, the mechanical energy of a system ______________ only if the system does _____________ on something else or energy is added from an outside source.

9. Conservation of Mechanical Energy • Kinetic Energy = Potential Energy in steps ____ & ___. • Kinetic Energy is at its maximum in steps ____ & ____. • Potential energy is at its maximum in step _____. 3 2 4 1 5

10. How does work affect kinetic energy? • A _________ object has the capacity to do work due to its ___________________. • The factors that control the amount of work a moving object can do are the ____________ as the factors that control the kinetic energy the object has: _______ and __________. • To stop the marbles, the cups did __________________on the marbles to bring the kinetic energy to _________. • ____________ energy can also do _______.