Physics Principles: Work, Energy, and Machines Q&A

Fundamental Concepts of Energy and Work

• 1. Which of these is measured in joules? Energy
• 2. The two main types of energy discussed: Kinetic & Potential
• 3. The work-energy theorem: The net work done on an object equals the change in its kinetic energy.
• 4. Kinetic energy: The energy of movement.
• 5. The Law of Conservation of Energy: Energy can neither be created nor destroyed.
• 6. Potential energy: The energy of position.
• 7. Pendulum potential energy: Highest when at the top of its swing.
• 8. Inelastic collision: A collision where some energy is converted into other forms.
• 9. Chemical energy: Energy stored in chemical bonds.

Machines, Power, and Efficiency

• 6. Which machine has 100% efficiency? No real machine has 100% efficiency.
• 7. Rube Goldberg: Famous for drawing pictures of complex ways to perform simple tasks.
• 8. Artificial joints: Commonly made from titanium.
• 9. Power definition: The amount of work done in a certain amount of time.
• 10. Force vs. Displacement graph: The area under the curve represents work.
• 11. Energy and Work: They share the same units.
• 12. Units for power: Watts.
• 13. Wheel and axle example: A door knob.
• 14. Ideal machine characteristics: Work input = work output; MA = IMA; Efficiency = 100%.
• 15. Lab priority: Safety.
• 16. Molecular digestion force: Electromagnetic.
• 17. Horizontal work calculation: Tcosθ (where T is tension and θ is the angle).
• 18. One thousand watts: A kilowatt.
• 19. Single pulley benefit: Allows for a preferred direction of motion.
• 20. Machine function: Eases the load by changing the magnitude or direction of force.
• 21. kW-h utility billing: We are paying for energy.