Types of Simple Machines A 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 Machines 1. Lever ____ 2. Pulley ____ 3. Wheel & Axle ____ 4. Inclined Plane ____ 5. Screw _____ 6. Wedge ____ Match the tool... A. Knife B. Crowbar C. Pencil SharpenerD. Elevator E. 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
1st Class Lever Fulcrum is located between the input and output forces Examples: Crowbar Seesaw Scissors are two class 1 levers
2nd Class Lever Effort and fulcrum are on opposite sides, load is between them Examples: Wheelbarrow Bottle opener
3rd Class Levers Effort 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? ________ Lever Animations at http://www.technologystudent.com/forcmom/lever1.htm 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 ]
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 smaller 1 pulley = 100 N 2 pulleys = 50 N 3 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.
IMA = length of slope height of slope Which of the following designs will produce the greater mechanical advantage?
http://youtu.be/suDJARX0nMA 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 ____________________
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 sides Examples: Axes, knives, chisels
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.