1 The Physics of Toys (and Space) Addendum to curriculum for Ms. Decker’s 2 nd Grade Class Jamestown Elementary By Darren McKnight Spring Force and Friction 2.Energy and Machines

2 Force – Key Points What is a force? Why does gravity exert a force on you? If an object is not moving does that mean that there are no forces on it?

3 Force – Key Points Answers What is a force? –Something that pushes or pulls you Why does gravity exert a force on you? –Two objects with mass attract each other If an object is not moving does that mean that there are no forces on it? –It may but it probably means that the forces acting an object cancel out

4 Forces The man is standing still. Are there any forces on the man? If so, draw them. floor

5 Forces The force due to gravity is pushing him down. Is there another force? Gravity

6 Forces The other force is the floor pushing back! Which force is greater? Gravity Floor

7 Forces The force due to gravity is the same in size, but opposite in direction, to the force by the floor!!!! Floor Gravity

8 Gravitational Force - Questions So what causes a gravitational force? Is there a gravitational force on the moon? –Is it larger or smaller than the gravitational force on the Earth?

9 Gravitational Force - Answer So what causes a gravitational force? –Two objects are attracted to each other Object 2 (has mass) Object 1 (has mass) F1F1 F2F2 F 1 = F 2

10 Gravitational Force Gravitational force keeps us “stuck” to the Earth!!! We actually pull on the Earth but the Earth is too big to move!!! Earth Person F F F person = F earth

11 Gravitational Force - Questions Is there a gravitational force on a person standing on the moon? –Is it larger or smaller than the gravitational force on the Earth? –Why?

12 Gravitational Force - Answers Is there a gravitational force on the moon? –Is it larger or smaller than the gravitational force on the Earth? The gravitational force is smaller on the moon. –Why? The moon is smaller (less massive) than the Earth.

13 Force – Key Points What is a force? Why does gravity exert a force on you? If an object is not moving does that mean that there are no forces on it?

14 Final Force Example Ms. Decker at the Pool. - What forces are acting on Ms. Decker as she stands on the end of the diving board? - Draw them.

15 Final Force Example Ms. Decker at the Pool. - What forces are acting on Ms. Decker as she stands on the end of the diving board? Force from diving board Force from Ms. Decker (gravity)

16 Final Force Example Ms. Decker at the Pool - Which force is greater?. Force from diving board Force from Ms. Decker (gravity)

17 Final Force Example Ms. Decker at the Pool -Which force is greater? They are equal since Ms. Decker is not moving. Force from diving board Force from Ms. Decker (gravity)

18 Final Force Example Ms. Decker at the Pool. -What if Ms. Decker walks off the end of the diving board? - Why?

19 Final Force Example Ms. Decker at the Pool. -What if Ms. Decker walks off the end of the diving board? She starts to fall toward the water - Why? Gravity is still forcing down but there is no force from the diving board - Draw the forces on Ms. Decker.

20 Final Force Example Ms. Decker at the Pool. -Draw the forces on Ms. Decker. -Why does Ms. Decker continue to fall? Gravity Air Resistance

21 Final Force Example Ms. Decker at the Pool. -Why does Ms. Decker continue to fall? The force due to gravity is greater than air resistance force opposing her fall. - What happens when Ms. Decker hits the water. Gravity Air Resistance

22 Final Force Example Ms. Decker at the Pool. -What happens when she hits the water? She gets wet!!!

23 Friction – Key Points What is friction? What makes friction greater? What makes friction less?

24 Friction Rubbing – create heat or slow down motion or both –What are examples of friction?

25 Friction Rubbing” – create heat or slow down motion or both –What are examples of friction? Rubbing hands together to get warm Putting sand on the road to prevent cars from sliding Newspaper sliding across the driveway Any more?

26 Friction Two items determine the friction force –YES, FRICTION CREATES A FORCE!!! 1. Goes against the motion 2. Greater if surfaces are rough ; less is surfaces are smooth If we slid a book across the two surfaces below, on which one would the book go farther? A B

27 Friction If we slid a book across the two surfaces below, on which one would the book go farther? A Draw the forces on book. A B

28 Friction Draw the forces on book. A Table Book (gravity) Friction

29 Friction in Space Is there any friction in space? Is there any friction when objects come back from space?

30 Friction in Space Is there any friction in space? –No, no air or surfaces to slide against Is there any friction when objects come back from space? –Yes, the air creates a surface and a tremendous amount of heat when objects comes back to Earth. –Manned spacecraft have special heat shields so that they do not burn up!!!!!!! –Shooting stars are just cosmic “pebbles” burning up as they come into the Earth’s atmosphere

31 Reentering Space Vehicle

32 Friction – Key Points What is friction? –A force that opposes motion What makes friction greater? –Rougher surface What makes friction less? –Smoother surface

33 Friction – Final Example Draw the forces on the picture. Hint: The puck is slowing down as it moves across the table. How could you increase the distance the puck would slide? The puck is sliding this way…

34 Friction – Final Example Draw the forces on the picture. Hint: The puck is slowing down as it moves across the table. How could you increase the distance the puck would slide? Polish the table or polish the bottom of the puck – reduce friction!!!! The puck is sliding this way… Force from table Force due to gravity Friction

35 Friction Lab We will slide three pucks at the same speed and measure how far they go We will plot the data and make observations Why might different pucks go different pucks go different distances?

36 Friction Lab Why might different pucks go different distances? –The bottom surfaces might be smoother or rougher than the others Everyone will record all of the data –I will call off distance traveled and puck letter (A, B, or C) Who wants to volunteer to slide the puck?

37 Friction Lab Data A B C Puck 18ft 15ft 12ft 9ft 6ft 3ft For example, the plot above shows puck A going 10ft and 15ft while puck B went 6 ft and 9ft X X X X

38 Friction Lab Data A B C Puck 18ft 15ft 12ft 9ft 6ft 3ft Which puck traveled the farthest?________ What does that mean?___________________________ Which puck had the most friction?_________

39 Big Word of the Day A surface that is very rough means it has a high coefficient of friction! Very impressive word to use at home! –“Gee Mom, our tires have a very high coefficient of friction!” –“Hey Dad, that icy road has a very low coefficient of friction!”

40 The Physics of Toys (and Space) Addendum to curriculum for Ms. Decker’s 2 nd Grade Class Jamestown Elementary By Darren McKnight Spring Force and Friction 2.Energy and Machines

41 Potential and Kinetic Energy – Key Facts Potential energy – “stored” energy –How can we “store” energy? Kinetic energy – energy of movement –How is potential energy converted into kinetic energy? What is work? –Exert a force over a distance

42 Potential Energy Does the ball have any stored energy here?

43 Potential Energy Does the ball have any stored energy here? NO YES, we moved the ball against gravity (did work)

44 Force Review What forces are acting on the ball while we hold it still above the floor? Draw and label them.

45 Force Review Which force is greater? They are the same, that is why the ball is not moving!!! Force of the hand Force due to gravity

46 Potential Energy What happens when we let go of the ball? If the ball is to move show the direction of the ball. Label the forces on the ball!!!!

47 Potential/Kinetic Energy What happens when we let go of the ball? It starts to fall – has kinetic energy If the ball is to move show the direction of the ball. Label the forces on the ball!!!! Gravity is larger force than air resistance velocity Gravity Air resistance

48 Potential and Kinetic Energy – Key Facts Potential energy – “stored” energy –How can we “store” energy? Kinetic energy – energy of movement –How is potential energy converted into kinetic energy? What is work? –Exert a force over a distance

49 Swing Set and Energy Does a swing have any kinetic energy when it is sitting still unused? How about potential energy? KE _____ PE _____ Does a swing have any kinetic energy when it is pulled up? How about potential energy? KE _____ PE _______

50 Swing Set and Energy Does a swing have any kinetic energy when it is sitting still unused? How about potential energy? KE __no_ PE _some_ Does a swing have any kinetic energy when it is pulled up? How about potential energy? KE __no_ PE __more___

51 Swing Set and Energy What happens when you let go of the swing to the kinetic energy and potential energy? KE _____ PE _____ As the swing gets to the bottom again what is the energy? KE _____ PE _______

52 Swing Set and Energy What happens when you let go of the swing to the kinetic energy and potential energy? KE _starts_ PE _goes down_ As the swing gets to the bottom again what is the energy? KE _maximum_ PE _minimum_

53 Swing Set – Exchanging Energy So as the swing oscillates (another big word to use at home – means “go back and forth”) it exchanges kinetic energy for potential and back again Why does the swing always eventually stop?

54 Swing Set – Exchanging Energy Why does the swing always eventually stop? –Friction from where the chain attaches to the swing set –Air resistance

55 Springs What are springs used for? Can you describe how a spring “stores” energy? Can you describe how a spring releases kinetic energy?

56 Spring as a “Worker” SpringPEKE RelaxedNone SqueezedMaximumNone ReleasedSome Back to MiddleNoneMaximum V V

57 Spring Lab You will observe –1. How potential energy is stored in a spring (compress the spring) and –2. Then converted into kinetic energy (the spring flies up with some velocity) and –3. Then converted back into potential energy (jumping up a certain distance)

58 Spring Lab Step 1: Compress spring a certain amount –A little (first mark) –A lot (second mark) –All the way (third mark) Step 2: Let the spring go! Step 3: Record how high up the spring goes on the stick –Stick is marked in one foot sections by color Work in pairs and put answers on the empty table

59 Data Collection for Spring Lab Press Down the SpringHow High it Jumps A littlebrown A little A lotpink A lot All the wayred All the way The table above shows three example experiments: when the spring was pushed down a little it stayed in brown, for “a lot” it went to pink, and when compressed “all the way” it went all the way to the red.

60 Data Collection for Spring Lab Press Down the SpringHow High it Jumps A little A lot All the way Explain what is happening in your own words:_________________ ______________________________________________________

61 Observations from Spring Lab The more you compress the spring the farther up it jumps –Give it more potential energy (stored in the spring) then it has a greater kinetic energy (shoots up higher) What causes the spring to slow down and eventually stop?

62 Observations from Spring Lab What causes the spring to slow down and eventually stop? –Gravity is acting down on the spring slowing it down –There is probably some friction between the spring and the stick

63 Satellites in Orbit Satellite is an object that goes around and around another object –The moon is a satellite of the Earth –The space shuttle is a satellite when it goes into space –The Earth is a satellite around the Sun A satellite in orbit is much like a swing!!!

64 Satellites in Orbit A B At point A the satellite is closest to the Earth and at Point B it is farthest from the Earth. What does that mean about its potential energy at points A and B?

65 Satellites in Orbit A B What does that mean about its potential energy at points A and B? Lowest potential energy at A and highest at B So what do you think is true about the kinetic energy at points A and B?

66 Satellites in Orbit A B So what do you think is true about the kinetic energy at points A and B? The kinetic energy is smallest at point B (slowest) and largest point A (fastest)

67 Machines – Key Facts What is a machine? Name some examples?

68 Machines – Key Facts What is a machine? –Something that uses energy to do useful activities Name some examples? –Levers –Wheels and axles –Pulleys –Inclined planes –Screws

69 Space Machines Momentum wheel – spin up a wheel to keep an object oriented Rocket – burn fuel, send exhaust out back so rocket moves forward Solar Panels – convert sunlight into electricity

70 Space Machines - Rockets

71 Space Machines - Satellites

72 Space Machines - Satellites Hubble Space Telescope

73 Releasing The Hubble What kind of machine picked up the Hubble and put it into space?

74 Space Machines - Satellites Hubble Space Telescope – broken into pieces

75 Space Machines on Moon or Other Planets Moon Mars

76 Space Physics – Overall Example Forces Energy – Potential and Kinetic Machines Friction

77 Rocket on the Launch Pad What forces are acting on the rocket? Draw on the forces.

78 Rocket on the Launch Pad What forces are acting on the rocket? Force due to gravity Force from the ground gravity Ground

79 Rocket on the Launch Pad What will happen when the rocket starts? Draw on the forces.

80 Rocket on the Launch Pad What will happen when the rocket starts? Force from the rocket is bigger than the force due to gravity and the air resistance rocket gravity Air resistance

81 Releasing the Satellite When the rocket gets into space how might the satellite be pushed away from the rocket? –Hint: What lab did we do where we store potential energy in a simple device that was later turned into kinetic energy?

82 RIGHT!!!! Springs are Used Last rocket springs The cover also needs to be taken off… How? Why do you think we needed a cover?

83 Satellite Then Unfolds Using a Small Motor Now it continues to go around and around the Earth. What do we call that?

84 Satellite in Orbit Where the satellite is located right now, what can you say about the kinetic and potential energy of the satellite? ___________________________________________________

85 Satellite Reenters Eventually the satellite comes back to Earth – WHY?

86 Satellite Reenters Eventually the satellite comes back to Earth – WHY? Air resistance from the atmosphere will slow it down Maybe a rocket was fired to bring it back to Earth What happens to the satellite as it reenters?

87 Satellite Reenters What happens to the satellite as it reenters? –It heats up and slows down due to friction It might melt and burn up completely depending on what it is made of…. Now you know all about rocket, satellites, and space physics!!!!!

88 Physics and Science are Very Important – Explain what is happening around you everyday!

89 Miss Decker’s Class May 2001 Write your name here