THE INCLINED PLANE, WEDGE, AND SCREW. 



283 



THE INCLINED PLANE, WEDGE, 

 AND SCREW. 



The inclined plane is the most simple of all machines. It is a hard plane 

 surface forming some angle with a horizontal plane, that angle not being a 

 right angle. When a weight is placed on such a plane, a twofold effect is 

 produced. A part of the effect of the weight is resisted by the plane and pro- 

 duces a pressure upon it ; and the remainder urges the weight down the plane, 

 and would produce a pressure against any surface resisting its motion placed 

 in a direction perpendicular to the plane. 



Let A B, fig. 1, be such a plane, B C its horizontal base, A C its height, 

 and A B C its angle of elevation. Let W be a weight placed upon it. This 



Fig. 1. 



weight acts in the vertical direction W D, and is equivalent to two forces — 

 W F perpendicular to the plane, and W E directed down the plane. If a 

 plane be placed at right angles to the inclined plane below W, it will resist the 

 descent of the weight, and sustain a pressure expressed by WE. Thus, the 

 weight W resting in the corner, instead of producing one pressure in the di- 

 rection W D, will produce two pressures : one expressed by W F upon the 



