Simple Machines

The Lever

Lever Goals

Identify and draw the 3 classes of levers

Understand the 3 cases of ideal mechanical advantage

IMA>1

IMA<1

IMA=1

Know and understand how to apply to the 2 formulas for mechanical advantage

Levers are…

1 of 2 main types of simple machines. (Inclined plane is the other kind.)

A machine helps you use your energy more effectively.

used to multiply input force

used to change the direction of motion

Parts of a LeverFULCRUM – a support or pivot

OUTPUT FORCE (Resistance or load) – what you are trying to move

INPUT FORCE (Effort or applied force) – your effort or force that is applied to lift the load

Identifying Class of LeverFirst, Second, or Third

Three Types of Levers

Similarities/Differences Levers

Similarities Differences

Eureka! The Lever

http://www.youtube.com/watch?v=wV1pYkTtsxg&NR=1

Three Types of Levers

FOI or FLE

Ugh! How am I going to remember?

What is in between is the key to identity of the lever.

FOI or FLE

1. Fulcrum or Fulcrum

2. Output or Load

3. Input or Effort

First Class LeverInput force Output force

Example: First Class Lever

Example: First Class Lever

Example: First Class Lever

Real Life Examples

Can you locate the fulcrum?

Second Class Lever

Input force

Output force

Ugh! How am I going to remember?

What is in between is the key to identity of the lever.

FOI or FLE

1. Fulcrum or Fulcrum

2. Output or Load

3. Input or Effort

Example: Second Class Lever

Example: Second Class Lever

Example: Second Class Lever

Real life examples

Can you find the fulcrum?

Third Class LeverOutput force

Input force

Ugh! How am I going to remember?

What is in between is the key to identity of the lever.

FOI or FLE

1. Fulcrum or Fulcrum

2. Output or Load

3. Input or Effort

Example: Third Class Lever

Example: Third Class Lever

Example: Third Class Lever

Ideal Mechanical Advantage(Friction -not taken into consideration)

is the factor by which a machine multiplies the force put into it.

OR

# of times a force exerted on machine is multiplied by the machine

MA does not have units!

What people are most important to remember?

FoFi LiLo

http://www.youtube.com/watch?v=eAACaVQNsQs&feature=related

Learn to fly

IMA Levers: 2 Formulas

IMA (lever) = Li (length of input arm)

Lo (length of output arm)

IMA (lever) = Fo (output force)

Fi (input force)

Question #1

A construction worker uses a board and log as a lever to lift a heavy rock. If the input arm is 5 meters long and the output arm is 0.55 meters long, what is the ideal mechanical advantage of the lever?

Based on the IMA calculated above, what does this mean about the applied force (input force) and the distance?

Question #2

If the input force of a first class lever is 6 Newtons and the output force is 3 Newtons, then what is the ideal mechanical advantage of this machine?

Based on the IMA calculated above, what does this mean about the applied force and the distance?

Now that you know the IMA of the lever, approximately, where would you place the fulcrum?

Question #3

A first class lever used to lift a heavy box has an input arm of 5 meters and an output arm of 0.9 meters. What is the ideal mechanical advantage of the lever?

Based on the IMA calculated above, what does this mean about the applied force and the distance?

Question #4

If the output force of a first class lever is 10 Newtons and the input force is 20 Newtons, then what is the ideal mechanical advantage of this machine?

Based on the IMA calculated above, what does this mean about the applied force and the distance?

Now that you know the IMA of the lever, approximately, where would you place the fulcrum?

Question #5

What is the ideal mechanical advantage of a lever that has an input arm of 4 meters and an output arm of 3 meters?

Based on the IMA calculated above, what does this mean about the applied force and the distance?

Question #6

A lever with an input arm of 3 meters has an ideal mechanical advantage of 5. What is the output arm’s length?

Question #7

A lever with an output arm of 0.6 meter has an ideal mechanical advantage of 4. What is the length of the input arm?

Ideal Mechanical Advantage > 1

If MA > 1, then your input force is increased by machine and distance the object moves is less. Amount of effort you need to exert is less. The machine is really helpful in this situation

Advantage – less input force is required

Input force multiplied (by machine), distance is less

Trade increased distance for decreased input force

Ideal Mechanical Advantage < 1

If MA < 1,then…your input force is decreased by the machine, distance is greater.

amount of effort you put in is greater.

machine is not as helpful, but you can move the load a greater distance.

Advantage – greater distance

Input force decreased (not multiplied by machine), distance is greater

Trade multiplied force for greater distance

Ideal Mechanical Advantage = 1

If MA = 1, then input force is not multiplied by machine, the distance the load travels does not change, BUT the direction of the input force changes

Only advantage is change of direction of input force

Eureka! The Lever

http://www.youtube.com/watch?v=wV1pYkTtsxg&NR=1

Mechanical Advantage

Eureka - http://www.youtube.com/watch?v=oWiZ_5qvs7I&feature=related

First Class Lever

Mechanical Advantage (depending on the position of the fulcrum) can be…

<1 (fulcrum closer AF/effort/input force)

>1 (fulcrum closer load/output force)

=1 (fulcrum equally distant between the load and effort)

First Class lever is the most complicated

Second Class Lever

MA >1 (load/output force is between)

Third Class Lever

MA<1 (effort is in between)

What is wrong with this picture?