law of conservation of energy energy

Transcription

1 What happens when? 6.8A compare and contrast potential and kinetic energy 6.9 Law of Conservation of energy states that energy can neither be created nor destroyed.

2 How does it work?

3 Explanation If you pull a ball up and out and then release it, it falls back and collides with the others with a loud click. Then, only the ball on the opposite end jumps forward, leaving the others behind, hanging still. That ball slows to a stop and then falls back, and all five briefly touch before the first ball is pushed away from the group again. The law of conservation of energy states that energy -- the ability to do work -- can't be created or destroyed. Energy can, however, change forms, which the Newton's Cradle takes advantage of -- particularly the conversion of potential energy to kinetic energy and vice versa.

4 A little more When all five are at rest, each has zero potential energy because they cannot move down any further and zero kinetic energy because they aren't moving. When the first ball is lifted up and out, its kinetic energy remains zero, but its potential energy is greater, because gravity can make it fall. After the ball is released, its potential energy is converted into kinetic energy during its fall because of the work gravity does on it.

5 Videos: Mythbusters Newton s Cradle Physics of Newton s Cradle

6 FIB Notes Remember, if it is red, write it down!

7 What is ENERGY? Energy is the ability to do work. Everything that happens in the world uses energy! Most of the time we can t see energy, but it is everywhere around us! Energy is measured in the unit JOULE. Or J for short.

8 Law of Conservation of Energy States that energy is NEVER created or destroyed, it just changes form Energy can only be STORED or TRANFERRED.

9 This car uses a lot of energy Batteries store energy! Even this sleeping puppy is using stored energy. We get our energy from FOOD!

10 How is all energy divided? All Energy Potential Energy Kinetic Energy

11 What are Potential and Kinetic Energy?

12 Potential Energy is The energy stored in an object. "Potential" simply means the energy has the ability to do something useful later on.

13 Examples of Potential Energy: A stretched rubber band.. Water at the top of a waterfall.. Yo Yo held in your hand.. A drawn Bow and Arrow

14 The higher an object, the more potential energy. This is known as gravitational potential energy The more mass an object has, the more potential energy it has.

15 Which object has more potential energy? A B

16 ANSWER A This brick has more mass than the feather; therefore more potential energy!

17 Changing an objects height can change its potential energy. If I want to drop an apple from the top of one of these three things, where will be the most potential energy? A B C

18 ANSWER A The higher the object, the more potential energy!

19 Potential Energy Converted to Kinetic Energy happens When stored energy begins to move, the object now transfers from potential energy into kinetic energy.

20 Kinetic Energy Is The energy of a moving object. "Kinetic" means movement! When stored energy is being used up, it is making things move or happen.

21 Examples of Kinetic Energy:

22 The faster the object moves, the more kinetic energy is produced. The greater the mass and speed of an object, the more kinetic energy there will be.

23 When these objects move at the same speed, which will have more kinetic energy?

24 ANSWER The semi- truck has more mass; therefore, more kinetic energy!

25 An object has the MOST kinetic energy when it s movement is the GREATEST. When an object has the LEAST potential energy, it has the MOST kinetic energy.

26 A water bottle is knocked off a desk. When does the bottle have the MOST kinetic energy? A. At the top of the fall. B. In the middle of the fall. C. At the bottom of the fall.

27 C. At the bottom of the fall. The roller coaster has the most kinetic energy when its movement and speed are greatest, which is at the bottom of the fall right before it hits the ground. Remember, when an object has the LEAST potential energy is when it has the MOST kinetic energy.

28 Roller Coasters When does the car on this roller coaster have the MOST potential energy? AT THE VERY TOP! The HIGHER the car is lifted by the motor, the MORE potential energy is produced. At the top of the hill the car has a huge amount of potential energy, but it has very little kinetic energy.

29 As the cars accelerate down the hill the potential energy is converted into kinetic energy. There is very little potential energy at the bottom of the hill, but there is a great amount of kinetic energy.

30 Put together, it looks like this:

31 See if you can label the roller coaster with PE and KE:

32 Potential and Kinetic Energy Together nt_rollercoaster/

33 Check your Answers:

34 Just for fun! Wiley E Coyote? Eureka!

35 Potential and Kinetic Energy On the back of your FIB note page, make a T-chart. Label the left Potential and the right side Kinetic Card Sort

36 Potential and Kinetic Energy With your desk partner, sort the pictures into the correct categories. When done, raise your hand and I will check before your write them down! Card Sort

37 Place them in your binder