ENERGY. 



EXEKCISES. 



1. How many horse-powers in an engine that will raise 8,250 Ibs. 

 176 ft. in 4 minutes ? 



2. A ball weighing 192.96 pounds is rolled with a velocity of 100 

 feet a second. How much energy has it ? Ans. 30000 foot-pounds. 



3. A projectile weighing 50 Kg. is thrown obliquely upward with 

 a velocity of 19.6 in. How much kinetic energy has it ? 



4. A ten-pound weight is thrown directly upward with a velocity 

 of 225.12 ft. (a.) What will be its kinetic energy at the end of the 

 third second of its ascent? (&.) At the end of the fourth second of 

 its descent ? 



5. A body weighing 40 Kg. moves at the rate of 30 Km. per hour. 

 Find its kinetic energy. 



6. What is the horse -power of an engine that can raise 1,500 

 pounds 2,376 feet in 3 minutes? 



7. A cubic foot of water weighs about 62| pounds. What is the 

 horse-power of an engine that can raise 300 cubic feet of water 

 every minute from a mine 132 ft. deep ? 



8. A body weighing 100 pounds moves with a velocity of 20 miles 

 per hour. Find its kinetic- energy. 



9. A weight of 3 tons is lifted 50 feet. (#.) How much work was 

 done by the agent? (6.) If the work was done in a half -minute, 

 what was the necessary horse-power of the agent? 



10. How long will it take a two horse-power engine to raise 5 

 tons 100 feet ? 



11. How far can a two horse-power engine raise 5 tons in 30 sec. ? 



12. What is the horse-power of an engine that can do 1,650,000 

 foot-pounds of work in a minute ? 



13. What is the horse-power of an engine that can raise 2,376 

 pounds 1,000 feet in 2 minutes ? 



14. If a perfect sphere rest on a perfect, horizontal plane in a 

 vacuum, there will be no resistance to a force tending to move it. 

 How much work is necessary to give to such a sphere, under such 

 circumstances, a velocity of 20 feet a second, if the sphere weighs 

 201 pounds ? 



15. A railway car weighs 10 tons. From a state of rest it is 

 moved 50 feet, when it is moving at the rate of 3 miles an hour. 

 If the resistances from friction, etc., are 8 pounds per ton, how 

 many foot-pounds of work have been expended upon the car? 

 (First find the work done in overcoming friction, etc., through 50 ft. 

 which is 50 foot-pounds x 10 x 8. To this add the work done in 

 giving the car kinetic energy.) 



