2. LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END COMPUTER PRESENTATIONS FOR KS3 SCIENCE - PHYSICS ©2003, STEVE PARKER COMPUTER PRESENTATIONS FOR KS3 SCIENCE - PHYSICS ©2003, STEVE PARKER

3. 1 1 KS3 SCIENCE - PHYSICS KS3 SCIENCE - PHYSICS Gravity, Friction & Air Resistance Gravity, Friction & Air Resistance

4. GRAVITY 2 2

5. 3 3 As Sir Isaac Newton discovered, gravity is an attraction between any two bodies, which depends on their mass As Sir Isaac Newton discovered, gravity is an attraction between any two bodies, which depends on their mass

6. GRAVITY 4 4 Because the Earth is very massive, it pulls objects with a force of 10 Newtons for every Kg of the object’s mass Because the Earth is very massive, it pulls objects with a force of 10 Newtons for every Kg of the object’s mass

7. GRAVITY 5 5 Gravity pulls everything towards the earth, so “Projectiles” move in an arc Gravity pulls everything towards the earth, so “Projectiles” move in an arc

8. FRICTION 6 6

9. 7 7 “Friction” is the stickiness between two surfaces when they rub together, and it is a force that opposes movement “Friction” is the stickiness between two surfaces when they rub together, and it is a force that opposes movement “Static Friction” is when two surfaces grip as they try to move past each other “Static Friction” is when two surfaces grip as they try to move past each other

10. FRICTION 8 8 Without friction you would get nowhere when you tried to walk Without friction you would get nowhere when you tried to walk “Friction” is the stickiness between two surfaces when they rub together, and it is a force that opposes movement “Friction” is the stickiness between two surfaces when they rub together, and it is a force that opposes movement

11. FRICTION 9 9 On a smooth surface the opposing force is not strong enough to prevent movement - “Sliding Friction” On a smooth surface the opposing force is not strong enough to prevent movement - “Sliding Friction” “Friction” is the stickiness between two surfaces when they rub together, and it is a force that opposes movement “Friction” is the stickiness between two surfaces when they rub together, and it is a force that opposes movement

12. FRICTION 10 Lubrication is a slippery substance that goes in-between two surfaces to overcome friction, e.g. engine oil Lubrication is a slippery substance that goes in-between two surfaces to overcome friction, e.g. engine oil “Friction” is the stickiness between two surfaces when they rub together, and it is a force that opposes movement “Friction” is the stickiness between two surfaces when they rub together, and it is a force that opposes movement

13. AIR RESISTANCE 11

14. AIR RESISTANCE 12 When an object moves through a liquid or gas, there is friction, which creates “Resistance” When an object moves through a liquid or gas, there is friction, which creates “Resistance”

15. AIR RESISTANCE 13 Resistance can be reduced by having a “Streamlined” shape (a pointed front cuts through the liquid or gas more easily) Resistance can be reduced by having a “Streamlined” shape (a pointed front cuts through the liquid or gas more easily)

16. AIR RESISTANCE 14 Anything moving through the atmosphere will be affected by “Air Resistance” Anything moving through the atmosphere will be affected by “Air Resistance”

17. AIR RESISTANCE 15 Air resistance or “Drag” is caused by air moving around the object Air resistance or “Drag” is caused by air moving around the object Driving Force Air Resistance

18. AIR RESISTANCE 16 The faster the object goes, the stronger is the air resistance against it The faster the object goes, the stronger is the air resistance against it Driving Force Air Resistance

19. AIR RESISTANCE 17 Eventually the driving force and the air resistance are equal, so the object stops getting faster Eventually the driving force and the air resistance are equal, so the object stops getting faster Driving Force Air Resistance

20. AIR RESISTANCE 18 Driving Force Air Resistance There will therefore be a maximum speed through air, called the “Terminal Velocity” There will therefore be a maximum speed through air, called the “Terminal Velocity”

21. AIR RESISTANCE 19 Driving Force Air Resistance For a sky-diver, the terminal velocity is around 190 km per hr For a sky-diver, the terminal velocity is around 190 km per hr