Simple Machines

Types of Simple MachinesA simple machine does work with only one movement.  Simple machines can be combined to form more complex machines

We tend to think of machines as motorized devices with many moving parts.  In physics, a machine can be a simple item, like a shovel or a screw top lid

Overview of the 6 Simple Machines1.  Lever  ____2.  Pulley  ____3.  Wheel & Axle ____4.  Inclined Plane  ____5.  Screw _____6.  Wedge ____

Match the tool...

A.  KnifeB.  CrowbarC.  Pencil SharpenerD.  ElevatorE.  Wheelchair rampF.  Lid to a jar

Levers---- A bar that is free to pivot or turn at a fixed point.

--- The fixed point is called the FULCRUM

--- The output force produced depends on the length of the arm

http://youtube.com/v/E14T9en5mnc

Types of Levers

1st Class LeverFulcrum is located between the input and output forces

Examples:CrowbarSeesawScissors are two class 1 levers 

2nd Class LeverEffort and fulcrum are on opposite sides, load is between them

Examples:WheelbarrowBottle opener

3rd Class LeversEffort is applied between the fulcrum and the load

Ex.  Baseball bat, tweezers, fishing pole

Levers (3 Classes)Which class is a:

1.  Hammer  ___2.  Wheelbarrow  ___3.  Scissors ____ 4.  The claw of a hammer  ___5.  Refrigerator door ____6.  Shovel ____6.  Baseball bat ____

 

MEMORY TRICK

*remember the word FLEx*

1.  F = fulcrum in the middle

2.  L  =  load is in the middle

3.  E = effort is in the middle

                x is just for fun 

Ideal Mechanical Advantage of a Lever

IMA = Length of the input arm           Length of the output arm

What is the IMA of the lever shown below? ________

If the output arm was only 15 m, what is the IMA of the lever? _____

As you shorten the output arm,the mechanical advantage is  [ increased / decreased ]Lever Animations at  http://www.technologystudent.com/forcmom/lever1.htm

What is a pulley?

1.  Consists of a wheel and a rope (chain)2.  A fixed pulley is actually a modified first class lever.  It is fixed because part of it is attached and doesn't move.

Ex.  Elevators, dumb waiters, flagpoles

3.  Moveable pulleys multiply force

The Block and Tackle

System of pulleys consisting of fixed and movable pulleys.

Basically the weight of the object is spread over multiple ropes, meaning less force needs to be applied to raise it.

Essentially the rope is longer, and you must pull it a longer distance to raise the object.   Work = force x distance

How Stuff Works has an excellent explanation of this.

Multiple Pulleys Increase Mechanical Advantage

By spreading the force over a greater distance (using more than one pulley) you will reduce the effort required to raise an object. 

In each case, the length of the rope gets longer, and the effort required to lift the block gets smaller1 pulley = 100 N2 pulleys = 50 N3 pulleys = 25 N

Check for Understanding

1.  Which design will give you the greatest mechanical advantage?

2.  If F1 = 100 N, what is F2?  

3. Identify the movable and fixed pulleys in each design.

What is a Wheel and Axle?Shaft or axle attached to a larger wheel

Examples:  door knobs, screwdrivers, faucet handles, pencil sharpener

Mechanical Advantage of Wheel and Axle

IMA  = radius of wheel            radius of axle

You can increase the advantage by using a larger wheel

Gears = multiple wheels that interlock together, one turn of a larger wheel causes the smaller wheel to turn multiple times

In which figure(s) will the F rotate clockwise? _______

Inclined Planes - a sloping surface, such as a ramp, that reduces the amount of force required to do work

Like all machines, the principle is to spread the Force out over a longer Distance.

Ideal Mechanical Advantage

    IMA  = length of slope               height of slope 

Walking up the hill in a zigzag will require less effort than walking straight up the hill. 

Which of the following designs will produce the greater mechanical advantage?

IMA  = length of slope           height of slope 

1.  Energy and work are measured in ____________2.  For exertion, the greater the distance,                    the [ greater / lesser ] the force required.3.  The "sloping flat thing" is actually the ____________________

http://youtu.be/suDJARX0nMA

1. What is the pivot point of the teeter totter called? ________2. If you double the distance, you can _______ the forced needed.3.  Archimedes said: "give me a _______________ and I will move the _____________

1. The lever gave Professor B a mechanical _____________

2. Mechanical Advantage =  output divided by ___________

3.  The inclined plane is less efficient due to the force of                                                                         _____________

The Screw - an inclined plane wrapped in a spiral around a post

Examples: bolts, screws, lids, spiral staircase

The Wedge - an inclined plane with two sidesExamples:  Axes, knives, chisels

QUIZ TIME!

1.  What type of machine is a wheelchair ramp?

2.  What type of machine is a crowbar?  

3.  The fixed point for a lever to pivot is the _______.

4. If the LOAD is in the middle of a lever, it is called a  [1st, 2nd, 3rd ] class lever.

5.  What type of lever is pictured?         [ 1st, 2nd, or 3rd class ]

 6.  A system of pulleys that reduces the force needed to lift an object is called a ________________________

7.  Give an example of a wheel and axle: ____________ 8.  How can you increase the mechanical advantage of a wheel and axle?

9.  A ________ consists of multiple wheels that interlock 10.  What reduces the efficiency of an inclined plane? _____

11.  A wedge is an _____________________ with two sides.