18 ANSWERS TO PRACTICAL QUESTIONS 



23. A body falls in 5 seconds: with what velocity does 

 it strike the ground ? 



v = 32t. v = 32x5. v = 160 feet. 



74 24. Hoiv far ivill a body fall in 1O seconds? 



s = 16 2 . s = 16 x 10 2 = 1600 feet. 

 With what velocity ivill it strike the ground ? 



v = 32t. v = 32 x 10 = 320 feet. 



25. A body is thrown upward with a velocity of 11)2 

 feet the first second ; to what lieight will it rise ? 



Equation (1), v = 32t. 192 = 32t. t = Q sec. 

 (2), s = 16 2 . s = 16 x 6 2 = 576 feet. 



26. A ball is shot upward with a velocity of 250 feet ; 

 to what height ivill it rise? How long ivill it continue to 

 ascend ? 



Using equations (1) and (2), as in the last problem, we have 



t = 8 sec. 

 s = 1024 feet. 



28. Are any two plumb-lines parallel ? 



They are not, since they point to the earth's center of grav- 

 ity. No two spokes of a wheel can be parallel. 



29. A stone let fall from a bridge strikes the water in 

 three seconds. What is the lieight ? 



s = 16 2 . s - 16 x 3 2 = 144 feet. 



30. A stone falls from a church steeple in 4: seconds. 

 Wfiat is the height ? 



s = 16P. s = 16 x 4 2 = 256 feet. 



31. How far would a body fall the first second at a 

 height of 12,OOO miles above the earth's surface? 



(16,000 mi.) 2 : (4000 mi.) 2 : : 16 feet :x = l foot. 



32. A body at the surface of the earth weighs WO tons; 

 what would be its weight 1,OOO miles above ? 



(5000 mi.) 2 : (4000 mi.) 2 : : 100 tons : x - 64 tons. 



