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# Student Notes Y10

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### Student Notes Y10

1. 1. FORCE AND MOTION 1. Define a force as a push or a pull. 2. Describe the motion of an object using terms such as speeding up, slowing down, constant speed and stationary. Acceleration and deceleration. 3. Draw labelled diagrams showing all the forces acting on an object in motion (constant speed or accelerated) or an object at rest. Forces labelled as either thrust, friction, gravity and support. 4. Recognise that unbalanced forces will cause acceleration or deceleration (and change of direction or shape) 5. Recognise that constant speed is the result of balanced forces on an object. 6. Explain what is meant by friction and describe both the beneficial effects and the problems caused by friction. 7. Measure friction forces and their effects on an object’s motion. 8. Use force meters to measure forces on objects. 9. Describe weight as the gravity force on an object. 10. State the a force is measured in units called Newtons (N) and that 1N is the force needed to lift up 100g. 11. Calculate average speeds of objects using v = d/t. Whole number calculations only are required. 12. Experimentally determine the speed of an object by measuring both distance and time. 13. Describe the units of speed as m/s or km/h. 14. Draw a speed-time graph and recognise acceleration from the steepness of the graph line. 15. Describe the journey of an object from a given speed-time graph. Saturday, 13 March 2010
2. 2. Unmix the table MAKING A GLOSSARY WORD Ans Definition 1. Speed A. the unit of force 2. Acceleration B. a push or a pull 3. Deceleration C. when the forces that are in opposite directions are equal to each other 4. Constant D. when the forces that are in opposite directions are not equal to each other 5. Force E. a force, due to the earth, that acts downwards on all objects. 6. Newton F. The rate of decrease of speed 7. Balanced G. is good or helpful 8. Unbalanced H. the force which acts on an object in the forward direction 9. Thrust I. remains the same (doesn’t change) 10. Gravity J. a force that always opposes motion 11. Support K. a measure of the force due to gravity that acts on an object 12. Mass L. The rate of increase of speed 13. Weight M. A force due to the ground that prevents an object from falling 14. Friction N. the amount of matter in an object 15. Beneficial O. The rate at which distance is covered Saturday, 13 March 2010
3. 3. MAKING A GLOSSARY WORD Ans Definition 1. Speed A. The rate at which distance is covered 2. Acceleration B. The rate of increase of speed 3. Deceleration C. The rate of decrease of speed 4. Constant D. remains the same (doesn’t change) 5. Force E. a push or a pull 6. Newton F. the unit of force 7. Balanced G. when the forces that are in opposite directions are equal to each other 8. Unbalanced H. when the forces that are in opposite directions are not equal to each other 9. Thrust I. the force which acts on an object in the forward direction 10. Gravity J. a force, due to the earth, that acts downwards on all objects. 11. Support K. A force due to the ground that prevents an object from falling 12. Mass L. the amount of matter in an object 13. Weight M. a measure of the force due to gravity that acts on an object 14. Friction N. a force that always opposes motion 15. Beneficial O. is good or helpful Saturday, 13 March 2010
4. 4. EF FE A CT FO S RC OF E Saturday, 13 March 2010
5. 5. WHAT CAN A FORCE DO? Aim to investigate the effects of forces Equipment Ping pong ball (1 per group) Drinking straw (4 per group) Cans or some other object suitable for the goal posts (4 per group) Method - Part 1 1.By blowing through the straw apply force on the ball according to the instructions given (the diagrams are there to help you) 2.For each exercise describe the response of the ball to the force (what does the ball do?) Saturday, 13 March 2010
6. 6. (i) The ball is stationery F v=0 Key F = force v = speed The ball ___________________________________________________________ (ii) The ball is already moving in the direction of the force when the force is applied F v The ball ___________________________________________________________ (iii) The ball is already moving in the opposite direction to which the force is applied F v The ball ___________________________________________________________ (iv) The ball is already moving sideways to the direction in which the force applied F v The ball ___________________________________________________________ Saturday, 13 March 2010
7. 7. PING PONG SLALOM 1. This game involves setting up a slalom course (using objects from your pencil case) on your desk. 2. Each player blows through a straw to control the motion of the ball so that it weaves through the obstacles. 3. Each member of the group is timed using a stopwatch and given 3 turns. 4. The person with the lowest time wins the competition. Saturday, 13 March 2010
8. 8. EFFECTS OF A FORCE • A force is a push or a pull • You cannot see a force but you can sometimes see the effects of a force (what a force does). • Forces can be either contact (eg. leaning on a desk) or non-contact (eg. magnetic, gravity) A force can: 1.Cause movement in an object that is initially stationery 2.Change the speed of an object (speed it up or slow it down) 3.change the direction of an object. 4.change the shape of an object. 5.hold an object up (or lift an object) Saturday, 13 March 2010
9. 9. BA UN LA BA NC LA ED NC / ED Saturday, 13 March 2010
10. 10. Demo - lift force WHAT CAN A FORCE DO? Ping pong ball Hair dryer Observation Saturday, 13 March 2010
11. 11. BALANCED AND UNBALANCED FORCES BALANCED FORCES Back Forward Support force Friction force Driving force speed stays the same v OR speed equals ZERO (STANDING STILL) Force due to gravity BALANCED FORCES ARE EQUAL AND OPPOSITE TO EACH OTHER Draw diagrams showing all the forces acting in the following situations: 1.An aeroplane travels through the air in level flight at a constant speed. 2.A rock falls vertically with constant speed Saturday, 13 March 2010
12. 12. ARE NOT EQUAL UNBALANCED FORCES & OPPOSITE TO Back Forward EACH OTHER The object will speed up or it will slow down or change direction Support force Friction force Driving force speed increases in the forward direction Force due to gravity Support force For an object that is already moving in the Friction force Driving force forward direction speed decreases Force due to gravity Saturday, 13 March 2010
13. 13. Changing direction Car B is on a “collision course” car A’s path after the crash with car A Car B Car A Saturday, 13 March 2010
14. 14. Demo 1 BALANCED FORCES • There are often several forces acting on an object. • We see the effect of the combination of these forces often called the resultant force. • When there is no resultant force we say that the forces are balanced. Trolley Pulley v Hanging masses Lump of plasticene (balances friction) Copy and complete the following sentences (words in the list below can be used more than once): If the object is stationery it will ____________ ____________ under the influence of ___________ forces. If the object is moving at a ________ _________ then it will continue to __________ _____ ______ ____________ _____________ . Word list: stationery remain steady balanced a speed with move Saturday, 13 March 2010
15. 15. Demo 2 UNBALANCED FORCES Trolley Pulley v Hanging masses Copy and complete the following sentences (words in the list below can be used more than once): • If the object is moving in a forward direction at a steady speed, an unbalanced force in the direction in which it is moving will cause it to _____________ . • If the object is moving in a forward direction at a steady speed, an unbalanced force in the opposite direction to which it is moving will cause it to _____________ . • If the object is moving forward and a force acts at right angles to the motion of the object, describe the path of the object. Word list: decelerate accelerate Saturday, 13 March 2010
16. 16. Exercises FORCES AND MOTION For each of the following situations: 1. describe the effect of the forces on the motion of the person or object in your own words 2. draw the forces on the diagram if they have not already been drawn Saturday, 13 March 2010
17. 17. Each team is as strong as the other An incredible act of heroism ................. and all for a girl Questions 1. Describe the motion of the helicopter when the lift force is increased. 2. What happened to the helicopter when the skier jumped out? 3. Describe the forces on the skier at the instant he lands on the snow. Saturday, 13 March 2010
18. 18. WHAT TYPES OF MOTION RESULT FROM THE FORCES DRAWN? A ________________ B ________________ C _____________ Write a description of the types of motion illustrated in the spaces (above) Saturday, 13 March 2010
19. 19. WHAT TYPES OF MOTION RESULT FROM THE FORCES DRAWN? A Accelerating ________________ B ________________ C _____________ Write a description of the types of motion illustrated in the spaces (above) Saturday, 13 March 2010
20. 20. WHAT TYPES OF MOTION RESULT FROM THE FORCES DRAWN? A Accelerating ________________ B Constant speed ________________ C _____________ Write a description of the types of motion illustrated in the spaces (above) Saturday, 13 March 2010
21. 21. WHAT TYPES OF MOTION RESULT FROM THE FORCES DRAWN? A Accelerating ________________ B Constant speed ________________ C Decelerating _____________ Write a description of the types of motion illustrated in the spaces (above) Saturday, 13 March 2010
22. 22. FR IC TI ON Saturday, 13 March 2010
23. 23. Saturday, 13 March 2010
24. 24. Practical TAKE A DIVE blue tack nylon Saturday, 13 March 2010
25. 25. Results Shape of Average time Time taken to fall (s) Parachute taken to fall (s) Circular Square Rectangular Triangular Answer the questions (next slide) as full sentences Saturday, 13 March 2010
26. 26. In the space below draw a force diagram showing all the forces acting on the plasticene when it is dropping at a STEADY SPEED. Saturday, 13 March 2010
27. 27. AIR FRICTION and SPEED 20 N 1500 N 1000 N 1000 N Parachutist falling Parachutist falling rapidly at slowly at first SO the time that the parachute friction is small opens SO friction is large Saturday, 13 March 2010
28. 28. 36 km Space 1400 kmh -1 FELIX BAUMGARTNER Smash the sound barrier Earth Saturday, 13 March 2010
29. 29. WHAT DO YOU KNOW ABOUT FRICTION? Friction is a force that opposes motion. Can you give 5 examples of useful friction and 5 examples of friction which is a nuisance to us. “HOW USEFUL !!” “WHAT A NUISANCE !!” Saturday, 13 March 2010
30. 30. FRICTION & FOOTWEAR Aim to find the relationship between the shoe design and the friction force between the shoe and a flat surface. Force meter Force Shoe This end is higher Ramp inclined at an angle ϴ Background When the shoe is pulled up the ramp, friction is acting in the opposite direction. If the shoe is being pulled at a steady speed then the force of friction is equal to the pull force. The pull force is read from the force meter and this measurement will be equal to the friction between the shoe and the ramp. Saturday, 13 March 2010
31. 31. Method 1. Set your bench up so that it is angled upwards (shown above). 2. Mark out a zone about 60 cm along the benchtop using a whiteboard marker. This will be the zone within which you will pull the shoe along at a steady speed. 3. The reading on the force meter is taken and recorded next to the type of shoe that was tested (in the table below). 4. Three readings of force are taken for each type of shoe and the average force is calculated. 5. Steps 1 to 4 are repeated with at least 3 other different shoes. 6. The results are graphed. Results Type/ Average friction description of Force applied (Newtons) (N) shoe . . Saturday, 13 March 2010
32. 32. W EI GH T Saturday, 13 March 2010
33. 33. MASS AND WEIGHT The mass of an object, m is a measure of the amount of matter in that object. Units: kilogram, kg. The weight of an object, Fw is a measure of the force due to gravity on that object. Units: Newton, N. Practical: Finding the relationship between mass & weight Spring balance (reading in Newtons) Hanging masses (each mass, 50g) Method 1. Add masses to the hook of the spring balance one mass (50g) at a time 2. Each time you add a mass measure the weight (force due to gravity) acting on the mass and record it in the table below: Saturday, 13 March 2010
34. 34. Results Mass (g) 50 100 150 200 250 300 350 400 450 Weight (N) Plot a graph of Weight against Mass and then write a conclusion Saturday, 13 March 2010
35. 35. SO WHAT MAKES A GOOD GRAPH? Now let’s see what a good graph looks like Saturday, 13 March 2010
36. 36. SO WHAT MAKES A GOOD GRAPH? Heading Now let’s see what a good graph looks like Saturday, 13 March 2010
37. 37. SO WHAT MAKES A GOOD GRAPH? Heading Smooth curve/straight line (of best fit) to complete the graph Now let’s see what a good graph looks like Saturday, 13 March 2010
38. 38. SO WHAT MAKES A GOOD GRAPH? Heading Smooth curve/straight line Axes labelled (of best fit) to complete (with unit & quanitity) the graph Now let’s see what a good graph looks like Saturday, 13 March 2010
39. 39. SO WHAT MAKES A GOOD GRAPH? Heading Smooth curve/straight line Axes labelled (of best fit) to complete (with unit & quanitity) the graph Possibly a key Now let’s see what a good graph looks like Saturday, 13 March 2010
40. 40. SO WHAT MAKES A GOOD GRAPH? Heading Smooth curve/straight line Axes labelled (of best fit) to complete (with unit & quanitity) the graph Possibly a key Points plotted as crosses Now let’s see what a good graph looks like Saturday, 13 March 2010
41. 41. SO WHAT MAKES A GOOD GRAPH? Heading Smooth curve/straight line Axes labelled (of best fit) to complete (with unit & quanitity) the graph Possibly a Linear scale key Points plotted as crosses Now let’s see what a good graph looks like Saturday, 13 March 2010
42. 42. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: t (s) d (m) 0 0 1 3 2 6 3 9 4 10 5 10 6 8 7 6 8 5 9 5 Saturday, 13 March 2010
43. 43. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: t (s) d (m) 0 0 1 3 2 6 3 9 4 10 5 10 6 8 7 6 8 5 9 5 Saturday, 13 March 2010
44. 44. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: t (s) d (m) 0 0 1 3 2 6 3 9 4 10 5 10 6 8 7 6 8 5 9 5 0 1 2 3 4 5 6 7 8 9 10 Saturday, 13 March 2010
45. 45. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: t (s) d (m) 0 0 10 1 3 9 2 6 8 3 9 7 6 4 10 5 5 10 4 6 8 3 7 6 2 8 5 1 9 5 0 1 2 3 4 5 6 7 8 9 10 Saturday, 13 March 2010
46. 46. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 1 3 9 2 6 8 3 9 7 6 4 10 5 5 10 4 6 8 3 7 6 2 8 5 1 9 5 0 1 2 3 4 5 6 7 8 9 10 Saturday, 13 March 2010
47. 47. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 1 3 9 2 6 8 3 9 7 6 4 10 5 5 10 4 6 8 3 7 6 2 8 5 1 9 5 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
48. 48. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 1 3 9 2 6 8 3 9 7 6 4 10 5 5 10 4 6 8 3 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
49. 49. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 1 3 9 2 6 8 3 9 7 6 4 10 5 5 10 4 6 8 3 x 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
50. 50. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 1 3 9 2 6 8 3 9 7 6 x 4 10 5 5 10 4 6 8 3 x 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
51. 51. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 1 3 9 x 2 6 8 3 9 7 6 x 4 10 5 5 10 4 6 8 3 x 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
52. 52. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 x 1 3 9 x 2 6 8 3 9 7 6 x 4 10 5 5 10 4 6 8 3 x 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
53. 53. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 x x 1 3 9 x 2 6 8 3 9 7 6 x 4 10 5 5 10 4 6 8 3 x 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
54. 54. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 x x 1 3 9 x 8 x 2 6 3 9 7 6 x 4 10 5 5 10 4 6 8 3 x 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
55. 55. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 x x 1 3 9 x 8 x 2 6 3 9 7 6 x x 4 10 5 5 10 4 6 8 3 x 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
56. 56. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 x x 1 3 9 x 8 x 2 6 3 9 7 6 x x 4 10 5 x 5 10 4 6 8 3 x 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
57. 57. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 x x 1 3 9 x 8 x 2 6 3 9 7 6 x x 4 10 5 x x 5 10 4 6 8 3 x 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
58. 58. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: d (m) t (s) d (m) 0 0 10 x x 1 3 9 x 8 x 2 6 3 9 7 6 x x 4 10 5 x x 5 10 4 6 8 3 x 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
59. 59. DRAWING A GOOD GRAPH An example for all of us!! Draw a distance - time graph using the values in the table: A distance vs time graph d (m) t (s) d (m) 0 0 10 x x 1 3 9 x 8 x 2 6 3 9 7 6 x x 4 10 5 x x 5 10 4 6 8 3 x 7 6 2 8 5 1 9 5 x 0 1 2 3 4 5 6 7 8 9 10 t (s) Saturday, 13 March 2010
60. 60. SP EE D Saturday, 13 March 2010
61. 61. FORCES & GRAVITY Saturday, 13 March 2010
62. 62. CALCULATING AVERAGE SPEED distance travelled Average speed = time taken This formula allows you to calculate the average speed when the distance and time are known. It can be written using symbols: v= d where v = average speed (in metres per second, ms-1) t d = distance travelled (in metres, m) t = time taken (in seconds, s) Use this formula to calculate time when distance and speed are known t= d v and this formula to calculate distance when speed and time are known d= v x t “Here’s an easy way of remembering the formulae” d Just put your ﬁnger over the quantity you want to calculate and the v t formula appears Saturday, 13 March 2010
63. 63. Examples Calculate the average speed in each case: 1. A cyclist travels 100m in 5s. 2. A snail travels 1m in 200s. 3. An old man walks 300 cm in 2s. Calculate the distance travelled in each case: 1. A car travels at 10ms-1 for 10s. 2. A Rocket in space travels 1500ms-1 for 60s. Calculate the time taken in each case: 1. A car travels 100 m at an average speed of 10ms-1 2. A Rocket in space travels 30000 m at an average speed of 1500ms-1. Saturday, 13 March 2010
64. 64. FRICTION - GOOD & BAD Saturday, 13 March 2010
65. 65. MORE FRICTION Saturday, 13 March 2010
66. 66. SPEED CALCULATIONS [Wignall & Wales] Saturday, 13 March 2010
67. 67. Saturday, 13 March 2010
68. 68. GR AP M HS OT IO OF N Saturday, 13 March 2010
69. 69. “So what does speeding up look like on a speed - time graph?”? See for your self! Draw two graphs for the 40000N aeroplane taking off on a runway: (a) a distance - time graph (b) a speed - time graph 80000N 10000N Distance (m) Time (s) Speed (ms-1) 0 0 0 40000N 10 1 10 30 2 20 60 3 30 100 4 40 150 5 50 210 6 60 280 7 70 360 8 80 450 9 90 550 10 100 Saturday, 13 March 2010
70. 70. distance - time graph speed - time graph d (m) v (ms-1) 500 100 400 80 300 60 200 40 100 20 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 t (s) t (s) Questions 1. Sketch and label a line on your speed time graph that shows greater acceleration. 2. Sketch and label a line on your speed time graph that shows deceleration. The picture (above) shows the forces acting on the plane while it is on the runway. 3. Explain, in terms of the forces shown on the picture, why: (a) the plane speeds up on the runway (b) the plane remains on the runway before taking off Saturday, 13 March 2010
71. 71. CONSTRUCTING A SPEED-TIME GRAPH Equipment: lab trolley Cello tape ticker timer ticker tape Method scissors 30 cm ruler Part 1: Making a ticker tape record of motion 1. Check that the power pack power switch is in the “off” position. 2. Switch the voltage control to 8V. 3. Connect the leads of the ticker timer to the AC sockets. 4. Thread one end of your ticker tape through the ticker timer so that when the power pack is turned on and the tape is pulled through there is a trail of dots produced. Test this with a short piece of tape before you thread your 1.5 m length through. 5. Use Cello tape to attach the other end of the 1.5 m length of ticker tape to a lab trolley. 6. Position the trolley and the timer as shown in the diagram. 7. Push on the trolley with enough force that it travels for at least 1.5 m after the trolley has left your hand. Timer 8V Power pack On/Off Trolley Ticker tape Saturday, 13 March 2010
72. 72. Results t (s) d (m) v (ms-1) 4.6 cm 0 0.015 0.15 0.1 0.046 0.46 0.2 An example of how to mark your tape and record your results t (s) d (m) v (ms-1) t (s) d (m) v (ms-1) 0 1.1 0.1 1.2 0.2 1.3 0.3 1.4 0.4 1.5 0.5 1.6 0.6 1.7 0.7 1.8 0.8 1.9 0.9 2.0 1.0 2.1 Saturday, 13 March 2010
73. 73. Speed Speed - time graph for a falling mass (ms-1) 1.1 s 0.5 time 0.2 0.4 0.6 1.6 s (s) Saturday, 13 March 2010
74. 74. Summary UNDERSTANDING DISTANCE - TIME GRAPHS distance Standing still Horizontal Slowing down Curving down Constant speed (the steeper the line, the faster the movement) Straight Speeding up Curving up Saturday, 13 March 2010 time
75. 75. Summary UNDERSTANDING SPEED - TIME GRAPHS speed Constant speed Slowing down Speeding up time Standing still Standing still Saturday, 13 March 2010
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77. 77. SPEEDING UP AND SLOWING DOWN Consider the following speed - time graph of an object: v (ms-1) 5 4 For each time interval 3 (labelled A, B and C) 2 complete the table below: 1 A B C 0 1 2 3 4 5 t (s) Interval initial final Change in speed over how How much the speed speed (final - initial speed) many speed changes in seconds? one second A B C The ACCELERATION of the object A negative value is a DECELERATION Saturday, 13 March 2010
78. 78. ST AR TE R S Saturday, 13 March 2010
79. 79. DOUBLE TROUBLE Saturday, 13 March 2010
80. 80. PLAYING ON WORDS Saturday, 13 March 2010
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82. 82. READING ABOUT NEWTON Isaac Newton’s experience of an apple falling on his head encouraged him to think about forces. He had ideas about gravity force that are still important today. Newton was famous for his study of forces. He developed three laws which apply to forces. Newton’s first law stated that an object will remain stationery of travel at a steady speed unless acted upon by an unbalanced force. His second law stated that the object would accelerate in the direction of the unbalanced force. Newton knew that for any moving object there was often several forces acting together. The forces would be unbalanced if when they are added together they do not cancel each other out. It is easy to work out the unbalanced force: Saturday, 13 March 2010
83. 83. WHAT’S IN A NEWTON? 1. What is the shape of your graph? 2. What does your graph tell you is happening when you increase the amount of mass (hanging) evenly? 3. How many Newtons of gravity force act on every 100 g mass? 4. Work out how many Newtons of gravity force would act on every kg of mass. 5. How many Newtons do you weigh on Earth? 6. The gravity force per kilogram on the moon is one sixth that of Earth. How many Newtons would you weigh on the moon. 7. If you dropped an object on the moon, would you expect it to accelerate to the ground as much as if you dropped it on Earth? 8. Why do you think the force of gravity on the moon is less than the force of gravity on Earth? 9. When an object accelerates towards the ground, are the forces balanced or unbalanced Saturday, 13 March 2010
84. 84. PARACHUTING 1. Name two forces that act on a skydiver falling through the air. Air friction/resistance/drag and gravity 2. What is meant by the term “terminal velocity” the greatest speed achieved during a free fall 3. How does the air resistance on a falling object change as the object speeds up? It increases 4. Draw a picture showing the upward and downward forces on a skydiver that is falling with terminal velocity. drag 5. What force stays the same during skydiving? gravity Gravity Saturday, 13 March 2010
85. 85. Progress quizz - 3 Mar 1. instrument used to measure forces Force meter/spring scales 2. Name the unit of force Newton 3. Symbol for the unit N 4. 2 eg's of useful friction braking, parachuting, swimming, tyres 5. 2 eg's of friction which is a nuisance cars, planes, mechanical 6. Name the force that holds objects (on the ground) up support 7. Name the force (T...) that causes an object to speed up Thrust 8. 10 N ->, 2N <- ...... F's balanced/unbalanced Unbalanced 8N 9. Overall force 10. What happens to the air friction as an object falls faster. Increases Saturday, 13 March 2010
86. 86. UNDERSTANDING THE DISTANCE-TIME GRAPH A description of what the object is doing during each time interval: d (m) 5 A 4 3 B 2 1 A B C C 0 1 2 3 4 5 t (s) Distance-time graphs can show speed Steady speed Stopped 1. Copy the graphs 2. Use the labels in the box to label them Acceleration Deceleration d d d d t t t t Saturday, 13 March 2010
87. 87. QUICK QUESTIONS 1. Write the formula which allows you to calculate the: (a) average speed when the distance and time are known (b) time when the distance and average speed are known (c) distance when the time and average speed are known 2. Use the information in the table below to draw a distance - time graph t (s) d (m) 0 0 1 2 2 4 3 6 4 7 5 8 6 8 7 6 8 3 Saturday, 13 March 2010
88. 88. QUICK QUESTIONS Describe the motion that is pictured in the following graphs for the intervals shown: (a) A ___________________________________ d B ___________________________________ C ___________________________________ D ___________________________________ A B C D t (b) v A ___________________________________ B ___________________________________ C ___________________________________ D ___________________________________ A B C D t Saturday, 13 March 2010
89. 89. FORCES TO GRAPHS 1. What is the name of the force that drives objects in the forward direction 2. Name the force that always acts in the opposite direction to the object’s motion. 3. Name the force that slows down the motion of a parachute. 4. If an object is traveling at a steady speed, what can we say about the forces acting on that object 5. If an object is speeding up what can we say about the forces acting on that object 6. How does a force change the direction of an object? 7. Scientific word that means the same as 'speeding up" 8. What is a scientific word that means the same as "slowing down". 9. Sketch a distance time graph that shows an object traveling at a steady speed. 10. Sketch a distance time graph that shows an object stationery. Saturday, 13 March 2010
90. 90. PUTTING THINGS IN THE PICTURE Study the graph below and answer the questions which follow: d Which section/s of the graph shows the object: (a) at constant speed _______ C (b) stationery _______ (c) speeding up _______ A B D E (d) slowing down _______ (e) moving in the reverse direction _______ t v Which section/s of the graph shows the object: (a) at constant speed _______ (b) increasing in speed steadily _______ (c) decreasing in speed _______ B D E (d) increasing in speed at an increasing rate A ______ t Saturday, 13 March 2010
91. 91. WORKING OUT ACCELERATION Extra 4 experts Consider the following speed - time graph of an object: v (ms-1) 5 4 For each time interval 3 (labelled A, B and C) 2 complete the table below: 1 A B C 0 1 2 3 4 5 t (s) Interval initial final Change in speed over how How much the speed speed (final - initial speed) many speed changes in seconds? one second A B C Using the correct units of acceleration, write the acceleration of the object during each time interval (in the space provided below): A = ___________ , B = ____________ , C = ______________ Saturday, 13 March 2010
92. 92. EX ER CI S ES Saturday, 13 March 2010
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