iy8 GENERAL SCIENCE 



it on the desk is work. Carrying bricks or mortar up a 

 ladder is work. We do work when we lift a 2oo-pound 

 box into a wagon. We do four times as much work when 

 we lift a 4oo-pound box into a wagon as when we lift a 

 loo-pound box into the same wagon. We do four times 

 as much work when we lift a loo-pound box up four feet 

 as when we lift the same box up one foot. 



From these statements we see that to do work it is 

 necessary that the object be moved, that is, work is a 

 result and not an effort. Work is a result of force and 

 not force itself. The amount of work done depends 

 upon the amount of the force and the distance through 

 which the object is moved. To move a given object 

 ten feet requires twice as much work as to move the same 

 object five feet, but the force required is the sanie in each 

 case. Twice as much work is done when a loo-pound 

 object is lifted four feet as when a 5o-pound object is lifted 

 four feet; here the distances are the same but the forces 

 are different. 



Work is the result of a force moving through a distance. 

 Or, work = force multiplied by the distance the force 

 moved ; or, W = f X d (w= work, / = force, d = distance.) 



118. Unit of Work. Since force and distance can 

 be measured, work also can be measured. The unit of 

 work in the English system is the foot pound. The 

 foot pound is the work done when a " pound of force'' 

 moves through a distance of one foot. If we lift one 

 pound up one foot, we do a foot pound of work. To 

 lift 10 pounds five feet we do 50 foot pounds of work. 

 If a boy weighing 100 pounds climbs a ladder 10 feet 

 high, he does 1,000 foot pounds of work. 1 



1 In the metric system a unit of work is the gram centimeter. The 

 gram centimeter is the work done when a "gram of force" moves through 



