1. Force and Motion Mr. R. Gallagher

2. vs. I.Force vs. Motion 1.Force - a push or a pull - it is measured in the SI unit of Newton's “N” - example – pushing a desk or pulling a sled 2.Motion - a change in position with time -example – the sled moves from the top of the hill to the bottom

3. II.What is a Newton? *A Newton is what quantifies force (gives something a value). * One Newton is the amount of force required to give a 1-kg mass an acceleration of 1 m/s² *10N means 10 Newtons of force.

4. III.Balance vs. Unbalanced forces All objects have at least two forces acting on them, sometimes more Ex. Holding a book in the air –One force is gravity –One force is your muscles holding the book up in the air usuallyWhen forces are equal from opposite directions there is usually no movement and this is called balanced forces When one force is greater than another then the object moves in the direction the greater force is going and this is an unbalanced force

5. IV.Calculating and Measuring Force 1.Calculating force  Force is calculated mathematically by the formula F=ma  F= force  M= the mass of the object in Kg  A = the acceleration of the object in m/s²

6. Lets do some math! This sounds complicated but is really very simple to figure out. Example, Ken kicks a soccer ball that is 1.5Kg and it accelerates at a rate of 6m/s². With how much force did Ken kick the ball? F=ma F=? M= 1.5Kg (is this in the correct units?) A= 6m/s² *replace the letters with the numbers given

7. Lets do some math! When we rewrite the equation with the numbers it should look like this. F= (1.5Kg)(6m/s²) *what do the brackets mean? F= 9 Newtons

8. Calculating and Measuring Force (cont.) 2. Measuring force - Force is measured by using a force meter - it measures in Newton's “N”

9. V.Drawing a diagram to explain the forces on an object These are called free body diagrams Arrows are used to show the direction of the force. The arrows are labeled so you know what is causing the force. straight Ex. A basketball dropped straight down. F gravity F air resistance

10. Lets try a few 1.A book is at rest on a table top. Diagram the forces acting on the book. F gravity F normal (or the force from the table)

11. VI.Friction is a force that resists the motion of two objects that are in contact with each other Ex. A book sliding over your desk Ex. A Ball rolling across the floor Friction always works in the opposite direction of the moving object(s).

12. Friction (cont.) Friction occurs because every object has a surface All objects have tiny “lumps and bumps” on them that is the texture of surface These lumps and bumps catch as the two objects pass over each other

13. Friction (cont.) There is no such place as a perfectly frictionless environment Even in outer space there are tiny particles (micrometeorites) that cause friction The rougher the surfaces in contact the greater the friction (texture of the surfaces) The greater the weight the greater the friction Surface area does NOT affect friction

14. VII.Two kinds of Friction A.Static Friction  The friction that exists between two surfaces that are not moving relative to each other.  Notice that you need to push hard to get an object to start moving  When the object is still you are overcoming the static friction B.Kinetic Friction  The friction that exists between two surfaces that are moving relative to each other  Notice that once you get an object moving it takes less force to keep it moving  When the object is moving you are pushing against the kinetic friction

15. Signs of Friction When two surface rub they wear down faster Heat Reduce friction by : –Lubricant –Replace sliding with rolling

16. VIII.Drag Drag is the mechanical force created when a solid object moves through a fluid (a fluid can be a liquid or a gas) Is a specific form of friction Ex. A plane moving through air Ex. A swimmer moving through water

17. IX.Gravity A force that pulls anything with mass towards another thing that has mass –Matter – anything that takes up space and has mass –Mass – amount of matter in an object

18. A.Measuring mass and weight Gravity (cont.) a.Weight  A spring scale is used to measure weight (Newton's)  Weight depends on gravity  Therefore weight can change  The moons mass is 1/6 of the earth’s and therefore weight of objects on the moon are 1/6 of what they would be on earth b.Mass  A balance is used to measure mass (grams)  Can never be altered in an object without adding or taking away from the object

19. B.Newton’s Ideas on Gravity Gravity (cont.) a.The force of gravity is acting between every pair of objects in the universe b.The greater the mass of the objects the greater the force of gravity between them c.The greater the distance between objects, the smaller the force of gravity between them

20. X. Newton’s Laws of Motion Law #1 -An object in motion tends to stay in motion unless outsides forces act upon it -Sometimes referred to as the “Law of Inertia” -INTERTIA

21. Newton’s Laws of Motion Law #2 -The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. - the harder you kick a ball the faster and further it will go

22. Newton’s Laws of Motion Law #3 - For every action there is an equal and opposite reaction.

23. XI.Inertia The tendency for an object to stay in the state of motion that it is in Something that’s moving wants to keep moving and something that is at rest want to stay at rest

24. Flight (cont.) a)Forces acting on a plane: - lift - created by the wing - gravity/weight - force pulling down - Thrust - created by the jet engine or propellers - drag - air resistance against the plane

25. Flight (cont.) b.How does a plane create lift?  The wing moves through the air at a great velocity  Because of the shape of the wing the air that moves over the top moves faster than the air that moves under the wing  This creates an area of high pressure under the high and low pressure above the wing

26. Flight (cont.) b.How does a plane create lift? (cont.)  The area of high pressure tries to balance itself out and move to the area of low pressure  Since the wing is between where it wants to go it pushes up on the wing

27. XIII. Helicopters Their blades are in the shape of an airfoil (wings) They turn fast enough to create the same high and low pressure of a planes wing