No – you are NOT getting paid for this! Work, Power & Simple Machines No – you are NOT getting paid for this!

Video Work and Power TAKE NOTES http://app.discoveryeducation.com/player/view/assetGuid/F8D7ACC0-B7DE-4867-BBDD-E9FB87DE64C7

What is Work? Work means several different things in everyday life… You work on science problems. Your parents go to work. Your toaster doesn’t work. Taking out the trash is too much work. Work means only one thing in physics… Work is force times distance. To be exact – WORK is force times the distance moved in the direction of the force.

Calculating Work W = F x d The formula to calculate work is… W = F x d Units for Work are – Joules (J) or Newton-meters (Nm) Units for Force are – Newtons Units for Distance are - meters

Calculating Work - Continued Like some of the other formulas we have worked on during class – the work formula can be manipulated by using a triangle. So, to find FORCE, we need to DIVIDE work and distance. Divide Multiply W F = W d Joules or Newton Meters And, to find DISTANCE, we need to DIVIDE work by force. F d Newtons Meters d = W F

Calculating Work - Continued A box weighing 2.0 N is lifted 4m. How much work was done? Step 1 Read the problem. Draw a picture. Step 3 Set up the formula. Step 4 Substitute the numbers. Solve. Box Answer with units. Step 2 Write down what you know. What are you trying to find? 8Joules Formula Substitute Answer W = 2.0 N F = W = FXd W = 2.0 NX4m W = 8 Joules D = 4m

Do problems 1 & 2 on your notes.

What is Power? Power is … The rate at which WORK is done. a measure of the amount of WORK done in a certain amount of time.

Calculating Power P = W T P = F x d T Units for Power are – Watts The formula to calculate power is… P = W T P = F x d T Units for Power are – Watts Units for Work are – Joules Units for Time are - Seconds 1 Watt is = 1 Joule/sec

Calculating Power - Continued Use the triangle to manipulate the Power formula. So, to find WORK, we need to MULTIPLY power and time. W Divide Joules or Newton Meters W = P X T And, to find TIME, we need to DIVIDE work by power. P T Watts Seconds Multiply T = W P

Calculating Power - Continued A figure skater lifts his partner, who weighs 450 N, 1.0 m in 3 seconds. How much power is required to lift his partner? Step 1 Read the problem. Draw a picture. Step 3 Set up the formula. Step 4 Substitute the numbers. Solve. Box Answer with units. Step 2 Write down what you know. What are you trying to find? Formula Substitute Answer 150 Watts P = P = 450N X 1.0m 3 sec P = W T W = 450N X 1.0m P =150 Watts 3 sec T =

Do problems 3 & 4 on your notes.

What is a Simple Machine? Is a device that does work with only one movement. Helps us do WORK by reducing our EFFORT – not the amount of work done.

Types of Simple Machines LEVER – Board that rests on a turning or pivot point. Turning / Pivot point is called the FULCRUM The object the lever moves is the LOAD or the RESISTANCE. The EFFORT is the force used to move the object. The closer the resistance is to the FULCRUM, the easier it is to move.

Effort – what’s moving it Classes of Levers – First Class Levers Fulcrum is between the Resistance & Effort Resistance – what’s being cut Fulcrum – pivot point Effort – what’s moving it

Effort – what’s moving it Classes of Levers – Second Class Levers Resistance is between the Fulcrum & Effort Resistance – what’s inside Effort – what’s moving it Fulcrum – pivot point

Effort – what’s moving it Classes of Levers – Third Class Levers Effort is between the Fulcrum & Resistance Fulcrum – pivot point Effort – what’s moving it Resistance – what’s being pushed

If it were FRE you would remember! How Do I Remember the Classes of Levers? What is located in the middle determines the class of level. F First Class Lever R Second Class Lever E Third Class Lever If it were FRE you would remember!

Types of Simple Machines - Continued 2. INCLINED PLANE – Flat surface that is higher on one end Used to make things move from a higher to lower place or lower to higher place Examples: Ramps, Slides, Path up Hill, Ladders

Types of Simple Machines - Continued 3. WHEEL & AXLE – Rod that goes through wheel that lets the wheel turn. Used to help make things turn in circular motion Examples: Cars, Roller Skates, Door Knobs, Fans and Faucets Gears-toothed wheel and axle

Types of Simple Machines - Continued 4. SCREW – Inclined plane wrapped about a cylindrical post. Used to raise and lower things or hold objects together Has ridges – not smooth like a nail Examples: Jar lids, Light bulbs, and Spiral Stairs

Types of Simple Machines - Continued 5. WEDGE – Two inclined planes pushed that meet to form a sharp edge. Used to split two things apart. Examples: Fork, Knife, Door Stop and Ax

Types of Simple Machines - Continued 6. PULLEY – Made of a wheel with a groove and a rope or chain that fits into the groove. One part of the pulley (usually the rope) is attached to the Load (Resistance) When you pull on the other side of the rope, the wheel turns and the load moves. Examples: Flag Poles, Sailboats, Blinds & Cranes

Block & Tackle – A system of ropes and pulleys that multiplies forces. Often seen in garages to lift engines out of cars.

What is a Compound Machine? Is a combination of two or more simple machines. Examples – Bikes, Forklifts, Pencil Sharpener