Even if Harry does not look tired and sweaty he has been performing work. Work is force moved through a distance. The work we have set out to do is to lift (move) 3500 N(force) 1 meter (Distance). Work Force X Distance

3,500N X 1m = 3,500Nm or 3,500 J (Joules)

 

Harry has not actually lifted the stone 1 meter but by using the lever, that work has been done. A force has been applied to the lever arm through a distance. Use the data from table 2 to calculate the work done by Harry on each of your successful tests.

• What do you notice about the amount of work done in each successful trial?
  
  
• Compare the effort distance (D_E) and effort force (F_E) in all trials. What happens to the amount of (F_E) as the (D_E) increases?
  
  
• Did you notice that when one amount changes the other amount will change in a specific way?

In science and mathematics we describe the relationship between two variables (like effort and resistance) as either "direct" or "inverse"

DIRECT	INVERSE
In a direct relationship, if one variable increases in value, the other variable also increases. (Make more money, pay more taxes)	In an inverse relationship, if one variable increases the other variable decreases. (Spend more money, savings goes down)

• Use the term "inverse" or "direct" to explain the relationship between effort force and effort distance as you adjusted your lever. (Use complete sentences)

• What are the advantages of using a lever to lift this stone? Hints: [Could you lift the stone without the lever or any other piece of equipment? In what direction did Harry apply the force?]

We can give these advantages a mathematical value. It is called Mechanical Advantage (MA).

The lever we have been using works when we apply the effort force (F_E) through a longer distance than the stone (F_R) moves.

We had to move a longer distance than the stone BUT we didn't have to apply as much force.

• Use the same data again to complete Table 4 in your packet.

• When you have completed Table 4, Calculate the MA both ways for each successful test.

• Can you draw any conclusions about the MA calculated using the forces and the MA calculated using the distances for each trial?

Comparing different trials:

• As the effort distance increases, what happens to the MA?

• As the effort distance increases, what happens to the effort force (F_E)?

• 

• With your lab partner, create a statement explaining the mechanical advantage of using a lever to lift a heavy mass.

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