1. TYPES OF FORCE

2. Force A force is defined as a push or pull that acts on an object A force can cause a stationary object to move, or it can accelerate an object that is already moving

3. Force Force makes motion happen Force can increase speed, decrease speed, or change the direction of movement of an object There are four different types of force: gravity, weight, friction, and torque All of these forces affect motion in different ways

4. Force The overall force that acts on an object is the NET force Balanced forces are forces that are acting in opposite directions but are of equal magnitude Unbalanced forces are forces that are acting in opposite directions but are of different magnitude. This is what causes objects to move

5. Gravity We looked at gravity briefly in our lesson on acceleration What can anyone remember from that? Let’s review

6. What is Gravity? The force by which objects tend to fall towards the centre of the earth

7. What is Gravity? Gravity is what holds the planets in orbit around the Sun and what keeps the Moon in orbit around Earth. The closer you are to an object, the stronger its gravitational pull is.

8. What is Gravity? How much gravity an object has depends on how big it is. To be specific, how much mass it has.

9. Who discovered gravity? The first person who dropped something heavy on their toe knew something was going on, but gravity was first mathematically described by the scientist Isaac Newton. His theory is called Newton's law of universal gravitation. Later, Albert Einstein would make some improvements on this theory in his theory of relativity.Albert Einstein

10. Gravity When an object is dropped, it falls. As it falls, it accelerates towards the earth The force of gravity increases as objects get closer to the center of the earth. Gravitational acceleration is the rate at which objects fall freely towards the earth (without any external factors). This rate is 9.8m/s²

11. LocationLatitudem/s 2 Equator0°9.7803 Sydney33°52′ S9.7968 Aberdeen57°9′ N9.8168 North Pole90° N9.8322

12. Air Resistance Air Resistance is the force that is opposite to gravity It is a force in an upward direction that will affect the speed at which gravity pulls towards the centre of the earth

13. Weight Weight is the force experienced by an object as the result of the earth’s gravitational pull Thus, the weight of an object differs depending on where it is located in the universe. In outerspace, a human would have no weight.

14. Mass VS Weight It is very important to understand the difference between mass and weight Mass indicates the amount of matter that makes up an object. If an object has a mass of 65kg, it will have a mass of 65kg on the moon Weight, however, IS affected by gravity and so it changes. Weight can also be described as how heavy something is. Weight is defined as Weight = Mass x Rate of Gravity These words are not interchangeable.

16. Force We have an equation to calculate force We know it as Force = Mass x Acceleration Force is in Newtons, Mass is in KG and Acceleration is in m/s² This is the same as saying Weight = Mass x Gravity Remember our weight on a scale has to do with the force of gravity acting on us

17. Friction Friction is a force that occurs when one object opposes or resists moving over another object If there was no friction, objects would continue to move at a constant speed forever (?) Friction causes moving parts on machines to wear out more quickly. It also changes some of the energy needed to do work into heat. This means it takes more energy to do the same amount of work

18. Friction Friction is reduced in machines by using oil and grease, using smooth surfaces, and using wheels, rollers, or bearings There are four different types of friction

19. Static Friction This is the friction that acts on objects that are not moving This type of friction is what is responsible for keeping us stationary Static friction keeps us in our seat, keeps our desks from moving, etc No heat or wear is generated

20. Sliding Friction Occurs when two surfaces slide one over the other It is the force resulting when pushing or pulling an object over a surface Example: moving boxes across the floor on moving day. Rubbing sandpaper across wood

21. Rolling Friction Occurs when an object rolls over a surface Friction or Contact is reduced because the wheels can roll over the surface easier Example: wheels on a vehicle while driving

22. Fluid Friction Resistance from liquids or gases The most common gas is air Water moving through a pipe is affected by friction An Olympic cyclist is affected by air Walking through water Stirring a thick batter

25. Torque Torque is a twisting force or effort that can act in either a clockwise or counterclockwise direction Using a wrench to loosen or tighten something is an example of torque

26. Torque Torque can be increased by applying more force OR by applying force farther away from the center of the object that you are trying to rotate

27. Torque Torque does not always result in motion. Thus, torque is not work

28. Torque When torque causes motion, the object where the force is applied will turn in a circle

29. Torque Torque = Force x radius Torque unit of measure is N-m ie radius is in metre and Force is in Newton

30. Example An ironworker applies 650N of force to the end of a 30cm wrench to tighten a bolt. How much torque is applied to the bolt? T = F x r r = 0.3 m F = 650 N T = 650 x 0.3 T = 195 N-m

31. T = F x r Two children are sitting on a seesaw. Calculate the distance the 500 N child should sit from the fulcrum to balance the seesaw