Do now 1.If I am traveling at 60 mph

for 3 hours, how far can I travel?

2.How much force is needed to lift a 5kg object 8 m?

3.How much power is created when I use 26 Joules in 13 seconds?

Announcements• Test on Friday

▫ Test is posted on my Wiki if you would like to look at it.

▫ I will have something for you guys as a reward for focusing during the test

Agenda

•We are going to learn very quickly about a couple of things still remaining in the unit:

▫Simple Machines▫Potential and Kinetic Energy

Are these machines?

Are these machines?

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Simple Machines

Ancient people invented simple machines that would help them overcome resistive forces and allow them to do the desired work against those forces.

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Simple Machines

•A simple machine is a device that helps make work easier to perform

•“Simple” because there is only one working part.

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Simple Machines

• The six simple machines are:▫ Lever ▫ Wheel and Axle ▫ Pulley ▫ Inclined Plane ▫ Wedge ▫ Screw

How does this effect the level of work?•While simple machines are simple and

lessen the workload, you are still doing the same amount of work.

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The Lever

•A lever is a rigid bar that rotates around a fixed point called the fulcrum.

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The 3 Classes of Levers

•There are 3 types of levers:

•The class of a lever is determined by the location of the effort force and the load relative to the fulcrum.

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Just so you can see…

To find the MA of a lever, divide the output force by the input force, or divide the length of the resistance arm by the length of the effort arm.

Lever Common Examples:

•Crowbar•Shovel•Back of a Hammer•See Saw•Bottle Opener

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Wheel and Axle

•A wheel with a rod, called an axel, through its center: both parts move together

•Examples: Doorknob, pencil sharpener, bike

Inclined Plane

•An Inclined Plane is slanting surface connecting a lower level to a higher level

•Things move up or down it

•Slide, stairs, ramp, escalator, slope

Pulley

•A pulley is grooved wheel with a rope or cable around it

•Moves things up, down, or across

•Curtain rod, tow truck, mini-blind, flag pole, crane

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Wedge•The wedge is a modification of the inclined plane. Wedges are used as either separating or holding devices.

Examples of Wedges:

•Car tire wedge•Door stop•Sledge Hammer

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Screw

•The screw is also a modified version of the inclined plane.

• It is considered a sixth simple machine

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Potential and Kinetic Energy

Energy

• Energy: how much work something can do

• measured in Joules, J• -Energy can change forms

II. Potential Energy

• Potential Energy: energy of position or “stored energy”

• Potential energy depends on mass and height.

II. Potential Energy

The person has more potential energy at the top of the stairs than at the bottom.

II. Potential Energy

Did the eggs we dropped have more potential energy at the 2nd or 3rd floor?

Kinetic energy

• Kinetic Energy: energy of motion

• Depends on: mass, velocity

III. Kinetic EnergyWhich has more kinetic energy, the regular car or the race car?

The race car has more KE because it has a higher velocity.

III. Kinetic Energy

Which would hurt more, getting hit by a 15 foot wave or a 2 foot wave?

The bigger wave would hurt more because even though they travel at the same speed, the bigger wave has more mass.

Can you think of any more examples of kinetic energy?

Prepare for a group activity!

Group Practice

•Write down 4 examples of potential energy, 4 examples of kinetic energy on your index cards

•Pass the cards to another group•Place the cards you receive in the right

category on your sheet•When you’re done, get your Independent

Practice!

Independent Practice

•Machines sheet