192 NATURE-STUDY LESSONS. 



3. Use the pry to roll a log or heavy barrel. 



4. {a) In rolling the log, on what does the lever rest 



and about what does it turn ? 

 (d) In this case, state the relative positions of the 

 weight, power and fulcrum. 



5. (a) Raise a plank or ladder upon its end by placing 



an end against some firm object. 



(d) Around what does the plank turn ? 



(c) Observe the relative positions of the weight, 

 power and fulcrum. 



There are three kinds of levers. 



1. Where the fulcrum is between the weight and the power; ir.^., the 

 pry used in raising the desk. This is a lever of the _^rsi kind. 



2. Levers used like the pry in rolling the log, where the weight is 

 between the fulcrum and the power. This is a lever of the second kind. 



3. Levers where the power is between the fulcrum and the weight ; eg., 

 the raising of a ladder by placing the end against the base of the building. 

 This is a lever of the third kind. 



B. To Discover tlie Principle of the Lever. 



6. («) Place one of the weights on each end of the 



ruler and balance it on the fulcrum. 

 (b) What distance is each weight from the fulcrum? 



7. (a) Place two weights side by side on one end of 



the ruler, and one weight on the other end, 

 and balance the weights. 1'"^ 



{V) Where does the ruler now balance ? 



{c) To which weight is the fulcrum nearer ? 



{d) How far is the fulcrum from the greater weight? 



(e) How far from the less weight ? 

 (/") Compare these distances. 



(^) Compare the weights. 



{h) Combine in one statement the relation between 



the weights and their respective; distances 



from the fulcrum. 



