FRICTION 



461 



SPINNING WHEEL 



A most useful application of simple machines. Spinning is now done 

 by much more complex machinery. 



their basis. These basic machines are the lever, the wheel 

 and axle, the pulley, the inclined plane, the wedge, and 

 the screw. 



Friction. If we attempt to slide a box along a level 

 floor, we find that we have to overcome resistance or do 



