62 



Common Science 



FIG. 30. But this is quite different. 



Do the points or handles move farther as you close the 

 shears? Which part closes with the greater force? 



Experiment 21. Use a Dover egg beater. Fasten a small 

 piece of string to one of the blades, so that you can tell how 

 many times it goes around. Turn the handle of the 'beater 

 around once slowly and count how many times the blade 

 goes around. Which moves faster, the handle or the blade? 

 Where would you expect to find more force, in the cogs or 

 in the blades? Test your conclusion this way: Put your 

 finger between the blades and try to pinch it by turning the 

 handle; then place your finger so that the skin is caught 

 between the cogs and try to pinch the finger by turning 

 the blades. Where is there more force? Where is there 

 more motion? 



Experiment 22. Put a spool over the nail which was 

 your fulcrum in the first two experiments. (Take the stick 

 off the nail first, of course.) Use this spool as a pulley. Put 

 a string over it and fasten one end of your string to the pail 

 (Fig. 32). Lift the pail by pulling down on the other end 



