Bell Work 4/25/12 – 6 min

Bell Work 4/25/12 – 6 min

A 30.0 lb monkey climbs 22.0 foot up a tree in 5.00 s.

1. What is his weight in N?2. How many meters of tree did he climb?3. How much work did he do?4. What was his power in Watts?5. What was his power in horsepower?6. How would carrying a bag of bananas have

affected the amount of work he did? Power?

Bell Work 5/9/13 – 5 min1. Another word for input is _____.2. Other words for output are _____ and _____.3. A first class lever consists of __, __, then __.4. A second class lever consists of __, __, then __.5. A third class lever consists of __, __, then __.6. Identify the class of the following levers. (some are >1 lever)

a. Crowbar b. Bottle openerc. Seesawd. Wrenche. Nail clippers f. Mousetrap

Bell Work 5/1/12 – 5 min1. Another word for load is _____.2. Another word for effort is _____.3. To identify the type of lever something is, you look at what is

in the middle. A first class lever has the _____ in the middle. A second class lever has the _____ in the middle. A third class lever has the _____ in the middle.

4. Identify the class of the following levers.a. Fishing rodb. scissors c. salad tongs

Turn in missing work by tomorrow, take a zero, or make other arrangements.

Bell Work 5/7/12 – 4 minutesIdentify the type of lever, find the mechanical

advantage, and find the missing force.

Bell Work 5/4/12 – 4 minutesIdentify the type of lever, find the mechanical

advantage, and find the missing force.

Bell Work 5/8/12 – 5 minBill (88.0 kg) climbs the 12.0 m wall in 55.0 s. His twin

brother Bart (88.0 kg) runs up the steps in 20.0 s. 1. Calculate Bill’s work & power.

2. Calculate Bart’s work & power.

Bell Work 5/9/13 – 5 min1. Another word for input is _____.2. Other words for output are _____ and _____.3. A first class lever consists of __, __, then __.4. A second class lever consists of __, __, then __.5. A third class lever consists of __, __, then __.6. Identify the class of the following levers. (some are >1 lever)

a. Wheelbarrow b. Rakec. Seesawd. Golf Clube. Shovelf. Nail clippers

Today you are going to…take notes on the simple machines

So you can…calculate the estimated & actual mechanical advantage

You’ll know you’ve got it when you can • Answer the questions at the end of class

• Machines can do 3 things– Change direction of force– Increase force & decrease distance– Decrease force & increase distance

• Mechanical advantage – how much machine multiplies force or increases distance– Ratio between output force and input force

• OR

– input distance and output distance– >1 1 multiplies input force, < 1 multiples distance &

speed

Simple MachinesSimple Machines

• Simple machines – most basic machines

• 6 types– 3 in lever family

• Simple levers (3 classes!)• Pulleys• Wheel & axle

– 3 in inclined plane family• Simple inclined Plane• Wedge• Screw

1. Simple Levers1. Simple Levers

3 parts of a lever: Input, fulcrum, & output

Input (aka effort) – force you’re applying

Fulcrum – pivot point, doesn’t move

Output (aka load, resistance) – what you’re lifting

3 classes of levers depending on location of input, fulcrum, & output

1st Class Lever

• 1st IFO – fulcrum in middle

• Most common type– May increase force or distance depending on

location of fulcrum – Always changes direction– Sea saw, hammer– Pliers – 2 1st class levers put together

2nd Class Lever

• 2nd FOI – Output – Increases force, decreases distance– Wheelbarrow, nutcrackers, hinged doors

3rd Class Lever

• 3rd FIO– Increases distance object is moved,

decreases force– Fishing rod, forearm

Estimated Mechanical Advantage of Levers

Identify the type of lever, find the mechanical advantage, and find the missing force.

Mechanical Advantage of LeversIdentify the type of lever, find the mechanical

advantage, and find the missing force.

Mechanical Advantage of LeversIdentify the type of lever, find the mechanical

advantage, and find the missing force.

Mechanical Advantage of LeversIdentify the type of lever, find the mechanical

advantage, and find the missing force.

Mechanical Advantage of LeversIdentify the type of lever, find the mechanical

advantage, and find the missing force.

1. Simple Levers1. Simple Levers• 1st Class OFA – Fulcrum in middle

– Most common type– Sea saw, crowbar– Pliers – 2 1st class levers put together

• 2nd FOA – output (load) in middle– Increases force, decreases distance– nutcrackers, hinged doors, wheelbarrow

• 3rd FIO – input (effort) in middle– Increases distance object is moved, decreases

force– forearm, baseball bat, hockey stick, rake

Pulley• Modified levers

– Middle of pulley is fulcrum of lever– Single fixed pulley mechanical advantage of 1

– both sides of lever same length

• Changes direction of force

Pulley

• Using more than 1 pulley at a time increases mechanical advantage

• Block and tackle – several pulleys put together in single unit

2. Pulleys2. Pulleys• Modified levers

– Center of pulley is fulcrum of lever– Single fixed pulley mechanical advantage of 1 –

both sides of lever same length– Changes direction of force– Using more than 1 pulley at a time increases

mechanical advantage– Block and tackle - several pulleys put together in

single unit

3. Wheel & Axle3. Wheel & Axle

• Lever/pulley connected to shaft– Steering wheel of car, screwdriver, crank– Multiples force (or distance)

3. Wheel & Axle3. Wheel & Axle• made up of two circular objects of different sizes

• axle (a rod) attached to the center of a larger wheel

3. Wheel & Axle3. Wheel & Axle

• two machines in one because you can use each part in different ways.

• roll something along wheels cut down on friction – Generally, the bigger the wheel = easier to roll

• like a “lever in the round” – door knob, sink faucet handle are round levers– fulcrum is in the middle where the axle turns

• Larger wheel diameter less force needed

• Larger wheel diameter have to turn further

Wheel and Axle• MA = Radius of wheel or = diameter of wheel

Radius of axle diameter of axle

• D.J. uses a crowbar to move a 600 N Dom. The effort arm is 80 cm long and the arm is 15 cm long. What type of lever is this? What is the mechanical advantage?

Inclined plane• a ramp used to reduce the effort needed to

raise or lower an object

• How can he make it take less force?

• MA =

Bell Work 5/9/12 – 5 minutesFind type & mechanical advantage.

Rank from least to greatest MA

Wedge• Wedge - simple machine used to separate

objects (or hold them together)– made up of one or two inclined planes that meet &

form sharp edge– Difference between wedge & inclined plane:

• Wedge moves, inclined plane doesn’t• Effort force applied in different directions

– a sharper wedge yields a larger force.

• Ex: knives, axes, forks and nails

Wedge

• Thinner, more mechanical advantage

• How could you increase the MA of an ax or knife?

• Sharpen it!

Pregunta

• How do you make going up a steep hill easier?

Screw vs. Mt. Road

Screw• Inclined plane wrapped around a shaft

• Thread – spiral ridge along edge of screw

• Pitch – distance between threads

• Smaller pitch– MA is higher/lower– Have to turn it less/more– Metal screws have smaller

pitch because metal is

harder than wood

Closure Questions

• What is a wedge composed of?• What 2 things can a wedge do?• Give 4 examples of wedges.• How can the MA of a wedge be improved?• How is a wedge different from an inclined plane?• What is a screw?• What is the pitch of a screw?• What is the thread of a screw?• Give one advantage and one disadvantage of having a screw

with a small pitch.• What type of screws typically have a smaller pitch?

Bell Work 5/11/12 – 4 min

• Chapman pushes a box 15.0 m across the floor with a constant force of 50.0 N. This takes him 7.5 seconds.

1.How much work did Chapman do?

2.What was Chapman ’s power?

3.What was Chapman ’s power in hp? (1 hp = 746 watts)

• Turn in human horsepower activity.

Bell Work 5/12/12 – 4 min• Complete this bell ringer on the same sheet as

you used yesterday.

• Michelle lifts a 5.0 kg box to a height 1.5 meters. This takes her 1.5 seconds.

1.How much work did Michelle do?

2.What was Michelle ’s power?

3.What was Michelle’s power in hp? (1 hp = 746 watts)

• Turn in human horsepower activity.

Compound Machines

STOP

Bell Work 4/27/12 – 2 min

Take everything off of your desk except a pencil, calculator, & blank piece of notebook paper.

Quiz 4/27/12 (makeup)1 hp = 746 Watts

Answer c.s. in complete sentences, show all work, and convert using the factor label method.

1. Define work. (c.s.)2. Define power. (c.s.)Katelyn lifts a 5 lb bowling ball 5.0 feet in 0.25 s. 1. How much work did she do?2. What was her power in Watts?3. What was her power in horsepower?

Machines can

– Change direction of force– Increase or decrease force

• 6 types of simple machines– 3 in lever family – 3 in inclined plane family

The Inclined Plane Family

Simple Inclined Plane

Lever!

• http://www.youtube.com/watch?v=V-f_SWEie8o&feature=fvwrel

• Split an apple with your bare hands!

Bell Work 5/7/12 – 4 minutesIdentify the type of lever, find the mechanical

advantage, and find the missing force.

Bell Work 5/8/12 – 4 minutesIdentify the type of lever, find the mechanical

advantage, and find the missing force.

Find the mechanical advantage of the wheel & axle.