Unit 1: Energy and Motion

Transcription

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2 4 Table of Contents Unit 1: Energy and Motion Chapter 4: Energy 4.1: The Nature of Energy 4.2: Conservation of Energy

3 4.1 The Nature of Energy Change Requires Energy Energy: ability to cause change. Types: Electrical, chemical, thermal, radiant, nuclear The SI unit of energy is the joule, abbreviated J.

4 4.1 The Nature of Energy Kinetic Energy Kinetic energy: energy of motion. Depends on: mass and speed

5 4.1 The Nature of Energy Kinetic Energy Example: Sarah has a mass of g and travels 100 m in 11.9 s. What is Sarah s KE? Practice Problems p. 102

6 4.1 The Nature of Energy Potential Energy Potential Energy: stored energy due to position. Ex: Apple in a tree

7 4.1 The Nature of Energy Elastic Potential Energy Elastic potential energy: energy stored by stretching or compressing Ex: rubber band, spring.

8 4.1 The Nature of Energy Chemical Potential Energy Chemical Potential Energy: stored in chemical bonds between atoms. Ex: Gasoline, food

9 4.1 The Nature of Energy Gravitational Potential Energy Gravitational potential energy (GPE): energy stored by objects above Earth s surface.

10 Practice Problems p. 104

11 4.1 Section Check Question 1 Energy is the ability to cause. A. change B. heat C. motion D. work

12 4.1 Section Check Answer The answer is A. Energy is the ability to cause change and has several different forms.

13 Conservation of Energy Changing Forms of Energy Energy can change forms. Ex: Light Bulb= electrical light/thermal

14 Conservation of Energy Transforming Chemical Energy Ex: engine= chemical kinetic/thermal.

15 Conservation of Energy Transforming Chemical Energy Ex: Plants convert light energy from the Sun into energy stored in chemical bonds in the plant. What other examples can you think of?

16 Conservation of Energy Conversions Between Kinetic and Potential Energy Mechanical energy: total amount of potential and kinetic energy in a system. mechanical energy = potential energy + kinetic energy

17 Conservation of Energy Energy Transformations in Projectile Motion

18 The Law of Conservation of Energy Energy can change form, but the TOTAL energy amount remains constant. Conservation of Energy The law of conservation of energy states that energy cannot be created or destroyed.

19 Conservation of Energy Converting Mass into Energy Nuclear Fusion: A special kind of energy conversion in the Sun and stars. Small amount of mass is transformed into a tremendous amount of energy. Reason sun has enough energy to light and warm Earth.

20 Conservation of Energy Nuclear Fission Nuclear Fission: nuclei are broken apart resulting in small amount of mass transforming to large amount of energy. -Allows nuclear power plants to generate electricity.

21 Conservation of Energy Energy Conversions in Your Body Your body stores energy in the form of fat and other chemical compounds. This chemical potential energy is used to fuel the processes that keep you alive, such as making your heart beat, movement, body temperature, etc.

22 Conservation of Energy Food Energy The food Calorie (C) is a unit used to measure how much energy you get from various food 1 C = about 4,184 J 1 gram of fat= 9 C of energy 1 g of carbohydrates/proteins = 4 C

23 Section Check Question 1 Mechanical energy is the total amount of in a system. A. kinetic energy B. momentum C. potential energy D. potential and kinetic

24 Section Check Answer The answer is D. Mechanical energy is the energy due to position and motion of all objects in a system.

25 Section Check Question 2 State the law of conservation of energy. Answer The law of conservation of energy states that energy cannot be created or destroyed.

26 Section Check Question 3 Friction converts energy into energy. A. electrical, thermal B. mechanical, thermal C. thermal, electrical D. thermal, mechanical

27 Section Check Answer The answer is B. Friction converts mechanical energy into thermal energy.