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- WORK AND ENERGY _ 33 
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18. A projectile weighing 12 lbs. bas a linear velocity of 2500 feet per second 
and an angular velocity about its axis of 500 revolutions per second. If its radius 
ration is 0°75 inch, what is the total kinetic energy of the projectile ? 
Apply the principle of the conservation of energy to find the velocity of 
ow circular cylinder after rolling a distance of 12 feet down a plane 
ed at a slope of 1 vertical in 5 horizontal. ; {Inst.C.E.] 
A fly-wheel (Fig. 27) mounted on a horizontal spindle in bearings is 
ted by winding a cord on the ones 
shing a weight to the cord, and allowing 
weight to fall to the ground. Inan 
actual experiment the ser Br weight was 21 
ibs., the total height of fall, 5 feet ; the 
se - whole time of rotation of the fly-wheel 
starting from rest was 70°25 seconds, and 
the total number of rotations of the fly- 
f 10 lbs. fall freely from rest so that i 
equi 
17. Two cylindrical tanks, A and B, of, respectively, 4 square yards and 
_ Square horizontal cross section, stand on the same floor and are 
mnected near the bottom by a narrow pipe. A at first contains 8 cubic yards 
of water, and B is empty. The water flows slowly into B. Find the amount of 
at which will have been generated when the water has ceased to flow and it 
has all come to rest. [Inst.C. E.] 
_ 18. Find the combined efficiency of a steam-engine and its boiler when the 
“Gen used is 14 lbs. per horse-power per hour, the calorific value of the coal being 
zy 
). The balls on the arms of a fly-press weigh 112 lbs, each, and they are 
ng with a velocity of 12 feet per second. How many ft.-lbs. of work 
ist be expended in bringing them to rest? If the die sinks ,; inch into the 
netal while the balls are being brought to rest, find the mean resistance to the 
_ motion of the die into the metal. 
20. A hammer used for driving a nail weighs 2 Ibs., and at the instant of 
riking the blow it is moving with a velocity of 16 feet. per second ; the blow 
- causes the nail to penetrate into the wood y*, inch. Find the mean pressure on 
at hdd ‘of the vial, . 
