Warm Up: (5 min) Go to my website: whitneystrickland.weebly.com Click on the assignments tab There is a link for today’s warm up beside Friday. Click on the link and play the Burglar Challenge. When you have completed the challenge, raise you hand to show me!

Review If the same stack of books is lifted the same distance, but one person does it twice as fast, which of the following is done twice as fast?? A. work input B. work output C. power D. efficiency

Today’s Objectives: 1) know how six different simple machines are used in every day life to make work easier 2) be able to calculate the mechanical advantage, and efficiency of machines.

The 6 Simple Machines Wedge Inclined plane Lever screw Wheel & Axle pulley screw Wheel & Axle

What is a machine? Something that makes doing work easier! Input Force: the force you apply to the machine Output Force: the force the machine applies to do work

What type of simple machine is this? Where is the Input force And where is the Output force?

How do machines work? Do they decrease the amount of work?? No Machines work by changing the size or changing the distance of the input force!!!

Review: Answer the questions in your notes 1. What is the work that you do on a machine? A. power B. work output C. work input d. lever 2. What is a device that makes work easier by changing the size or direction of the force? 3. When machines increase the size of the force exerted, what happens to the distance? 4. Does the total amount of work change when a machine is used?

Mechanical Advantage Mechanical Advantage : tells you how much the force increases. Mechanical Advantage (MA) = output force input force If you exert 30 N of force on a can opener and it exerts 60 N on the can, what is the can opener’s mechanical advantage?

Practice Problems Amanda uses a wheelbarrow to lift a load of bricks. The bricks weigh 600 N. With the wheelbarrow, Amanda can lift the bricks with as little as 120 N. What is the mechanical advantage of the wheelbarrow? A system of pulley allows a mechanic to lift a 1800 N engine. If the mechanic exerts 600 N of force to lift the machine, what is the MA? If the mechanic exerts 800 N of force to lift the machine, what is the MA?

Question The work output of a machine can never be greater than the work input. Work is never lost, so where does it go???

FRICTION!!!! Machines are not 100% efficient because some of the work done is used to overcome friction. Explain why work output can never be more than work input.

Mechanical Efficiency Compares the machine’s work output to the work input Equation: work output 100 % work input 1. A stage crew member uses a pulley system to lift scenery for the school play. If he does 600 J of work and the pulley does 300 J of work, what is the efficiency of the pulley system?

Complete these problems with your elbow partner 2. A ramp is used to load furniture onto a moving truck. The person does 1240 J of work pushing the furniture up the ramp, and the ramp does 822 J of work. Calculate the efficiency of the ramp. 3. To pull a nail out of a wood board a carpenter does 1000 J of work. The hammer he uses does 835 J of work. What is the efficiency of the hammer?