THE LEVER. 95 



21. If a power of 50 pounds acting upon any kind of machine, 

 move 15 feet, (a) how far can it move a weight of 250 pounds ? 

 (&.) How great a load can it move 75 feet ? 



22. If a power of 100 pounds acting upon a machine, moves with 

 a velocity of 10 feet per second, (a) to how great a load can it 

 give a velocity 125 feet per second ? (&.) With what velocity can it 

 move a load of 200 pounds ? 



23. A lever is 10 feet long ; F in the middle ; a power of 50 

 pounds is applied at one end ; (a) how great a load at the other end 

 can it support ? (6.) How great a load can it lift ? 



Ans. to (&.) : Anything less than 50 Ibs. 



24. The power-arm of a lever is 10 feet ; the weight-arm is 5 feet. 

 (a.) How long will the lever be if it is of the first class ? (&.) If it 

 is of the second? (c.) If it is of the third class? 



25. A bar 12 feet long is to be used as a lever, keeping the weight 

 3 feet from the fulcrum, (a.) What class or classes of levers may 

 it represent ? (&.) What weight can a power of 10 pounds support 

 in each case ? 



26. Length of lever = 10 feet. Four feet from the fulcrum and at 

 the end of that arm is a weight of 40 pounds ; two feet from the 

 fulcrum on the same side, is a weight of 1,000 pounds. What force 

 at the other end will counterbalance both weights ? 



27. At the opposite ends of a lever 20 feet long, two forces are 

 acting whose sum = 1,200 pounds. The lengths of the lever arms 

 are as 2 to 3 ; what are the two forces when the lever is in equi- 

 librium ? 



28. Length of lever = 8 feet, F in the centre. A force of 10 

 pounds acts at one end, one foot from it another of 100 pounds. 

 Three feet from the other end is a force of 100 pounds. Direction 

 of all forces, downward. Where must a downward force of 80 

 pounds be applied to balance the lever ? 



29. Length of lever db = 6^ feet ; fulcrum at c ; a downward 

 force of 60 pounds acts at a ; one of 75 pounds at a point d between 

 a and c, 2| feet from the fulcrum ; required the amount of equili- 

 brating force acting at &, the distance between & and c being feet. 



30. On a lever db, a downward force of 40 pounds acts at a, 10 

 feet from fulcrum c; on same side and 6^ feet from c, an upward 

 force, d, acts, amounting to 56 pounds ; distance be = 3 feet : a 

 downward force of 96 pounds acts at &. (a.) Where must a fourth 

 force of 28 pounds be applied to balance the lever, and (&) what 

 direction must it have ? 



31. A beam 18 feet long is supported at both ends ; a weight 

 of 1 ton is suspended 3 feet from one end, and a weight of 14 cwt.. 



