Unit 3 Work HS bk: Chapter 5 8 th gr. Bk: Chapter 12 1

The Big Idea: WORK Essential Question: How are work and energy related?

Georgia Performance Standards S8P2a: Explain energy transformation in terms of the Law of Conservation of Energy. S8P2b: Explain the relationship between potential and kinetic energy. S8P2c: Compare and contrast the different forms of energy (heat, light, electricity, mechanical motion, sound) and their characteristics. 3

SPS7. Students will relate transformations and flow of energy within a system. a. Identify energy transformations within a system (e.g. lighting of a match). b. Investigate molecular motion as it relates to thermal energy changes in terms of conduction, convection, and radiation c. Determine the heat capacity of a substance using mass, specific heat, and temperature. d. Explain the flow of energy in phase changes through the use of a phase diagram. 4 Georgia Performance Standards

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WORK Work—transfer of energy that occurs when a force makes an object move. For work to be done, something has to move and the motion must be same direction as force E2A42 6

WORK When work is done, a transfer of energy always occurs. Calculating Work Ex: You push a wheelbarrow with a force of 100N. You moved the wheelbarrow 5m. How much work did you do? 7 Work (joules) = Force (Newtons) X distance (meters) W = F X D W=F x D W= (100N) x (5m) W= 500J

WORK Power—the rate at which work is done. Ex.: You do 900J of work pushing a fridge. It took 5 seconds. What was your power? 8 Calculating Power Power (watts)= work (J)/time (s) P=w/t P= W/T P= 900J/5s P= 180 J/s P= 180 watts (W)

WORK Session Students will construct a Work Formula triangle foldable to help calculate work word problems. TOTD: Using the formulas, complete the word problems below the foldable. 9

The Big Idea: Human Lab Essential Question: Work…who needs it? Can you feel the power?

Human Lab: Can You feel the power? Do NOW: Finish your lab report from yesterday. Work with your same partner to discuss and answer the questions. 11

Chapter 12 Vocabulary Read Chapter 12, pages Define section 2 vocabulary Section 1 1.Work 2.Joule 3.power Section 2 4. Machine 5. Input force 6. Output force 7. Input work 8. Output work 9. Mechanical advantage 10. efficiency Section Inclined plane 12. Wedge 13. Screw 14. Lever 15. Fulcrum 16. Wheel and axle 17. Pulley 18. Compound machine

Web links b s/jams/science/forces-and- motion/simple-machines.htm s/jams/science/forces-and- motion/simple-machines.htm s/jams/science/forces-and- motion/simple-machines.htm b R1msPk R1msPk R1msPk b wsw0 wsw0 wsw0

Chapter 12 Work and Machines Big Idea: Using Machines Essential Question: What are some machines we use everyday to help make doing work easier?

Georgia Performance Standard s b b S8P3. Students will investigate relationship between force, mass, and the motion of objects. c. Demonstrate the effect of simple machines (lever, inclined plane, pulley, wedge, screw, and wheel and axle) on work. b b S8CS5. Students will use the ideas of system, model, change, and scale in exploring scientific and technological matters. a. Observe and explain how parts can be related to other parts in a system such as the role of simple machines in complex machines.

Using Machines b Machine—device that makes doing work easier. Machines make work easier by increasing the force that can be applied to an objectMachines make work easier by increasing the force that can be applied to an object Two forces are involved when machine does work.Two forces are involved when machine does work. (Fout) Output force—the force applied by machine (Fin) Input force— the force applied to machine

Using Machines b Mechanical Advantage—the ratio of the output force to the input force. Mechanical advantage = output force (newtons) input force (newtons) input force (newtons)Ma=Fout/Fin Efficiency—measure of how much work put into a machine is changed into useful output work by machines Machines can be made more efficient by reducing friction.

TOTD: There are machines all around us! Turn to your neighbor and discuss what kinds of machines you saw on your way to school today.

Chapter 12 Work and Machines Big Idea: Simple Machines Essential Question: Where can one find simple machines?

Simple Machines b Simple machine—machine that does work with only one movement of the machine. b All machines are made up of some of the 6 simple machines.

Simple Machines b Lever: b Lever: bar that is free to pivot around fixed point (fulcrum) 1 st1 st class lever—fulcrum is between the input force and the output force 2 nd2 nd class lever—output force is between fulcrum and input force 3 rd3 rd class lever—input force is between fulcrum and the output force.

Simple Machine b Wheel and Axle Consists of an axle attached to center of a larger wheel so that the wheel and axle rotate together.Consists of an axle attached to center of a larger wheel so that the wheel and axle rotate together.

Simple Machines b The screw Inclined planeInclined plane wrapped in a spiral around a cylindrical Post.

Simple Machines b Pulley Grooved wheel with a rope, chain or cable running along grooveGrooved wheel with a rope, chain or cable running along groove –Fixed Pulley—attached to something that doesn’t move –Moveable pulleys—one end of the rope is fixed and the wheel is free to move –Block and Tackle—system of pulleys consisting of fixed and moveable pulleys

Simple Machines b Inclined Plane—sloping surface, such as a ramp that reduces the amount of force required to do work.

Simple Machines b The wedge An inclined plane with one or two sloping sidesAn inclined plane with one or two sloping sides

Simple Machines b Compound Machine—2 or more simple machines that operate together

Why do we need simple machines? b Work means that we are exerting force and moving something. The 6 simple machines make our work easier. We won’t have to use as much force with our simple machines.

The Wheel and Axle b Two or more wheels are connected by an axle. b The wheel turns with or around the axle. b This car wheel has a big axle that it rotates around when the car moves.

Why do we need wheels? b Wheels help us move heavy objects. b They roll easily. b Did you know a doorknob is really two wheels connected by an axle? You can’t see the axle because it’s inside the wheels, but it’s there! b If there wasn’t an axle, the doorknob wouldn’t turn!

Another kind of wheel is called a gear! b A gear is a wheel with teeth. b The teeth fit in between each other and turn. b When one gear turns, its teeth push against the teeth of the other gear and they both turn. b There are gears on your bike, on a can opener and on an egg beater.

Pulleys b Lifting a bucket full of water is a lot of work! b A pulley is a wheel with a rope running over it. The wheel has a groove, called a sheave, and it keeps the rope from slipping off the wheel. b Remember, since there is a wheel in a pulley there also has to be an axle! b These two men are using a pulley to help them lift their heavy bucket.

Levers b There are three parts to a lever: b Load b Force b Fulcrum: support or balance

A seesaw is a lever b Let’s pretend you are riding a seesaw with your friend. b The center support is the fulcrum, which does not move. b The load is your friend sitting on one end. b You exert the force at the other end trying to lift your friend off the ground. b When you push down on your seat, (the force) you can lift your friend (the load) while the fulcrum acts as the pivot point, making the seesaw go up and down. b It’s easy to lift your friend this way instead of just picking her or him up by yourself!

The Wedge bAbA wedge is used to split, tighten, or secure a hold. bAbA wedge is usually a triangle shape with a sharp point. bIbIf you apply force at one end, the wedge will go between something, in this case an ax splits a piece of wood.

Where can we find wedges? b Wedges b Wedges that split: b Your b Your teeth! b Every b Every time you bite into something, you are using a wedge. b Wedges b Wedges that cut: b A b A saw! knife! b Wedges that tighten: b A doorstop to keep the door open. b Wedges that hold things together: b A nail holds wood to a wall or other wood.

The Screw b The three parts to a screw: b Head b Shaft b Tip b The head is the part that you exert a force on. b The shaft has ridges, called threads that wind around the screw. If it doesn’t have the threads, it is probably just a nail. b The tip is sharp.

How to use a screw: b Fasten two things together b When you turn it, the threads cut a groove in the material, making a hole. The groove holds the screw tightly in place. b To remove the screw you turn it the opposite way, you can’t just pull it out.

The Inclined Plane b It is a slanted surface or ramp. b It makes moving objects easier. b Roads are also inclined planes. Instead of going straight up, like this: roads go up at small angles, like the picture.

The 6 Simple Machines Lever Pulley Wheel and Axle Wedge Screw Inclined Plane