224 Agricultural Education. 



8. A waggon aud its load weigh together 8960 lbs., the diameter of 

 the " fore wheels " is 4 feet, and of the hinder ones 5 feet, and the 

 whole has to be dra\\Ti into a barn over a threshold 3 inches high. 



Required the force in lbs. that would be required to draw the fore 

 wheels over, and also the force necessary to draw the hind wheels over 

 the threshold, friction of all kinds being neglected. 



9.. A waggon 5 feet 6 inches high, weighing 20rV cwts., is laden 

 with 2 tons of sheaf-corn, the total height being 13 feet from the 

 groimd, aud the outsides of the tires of the wheels 5 feet apart ; the 

 load has shifted, and the centre of gTavity is found in a line at 2 feet 

 within the outside of the " near side " wheels, and at a height of 

 9 feet above the ground. 



Required the difference in level of a road or of a hill side when the 

 whole would be in equilibrium and just on the point of upsetting. 



10. An endless screw, consisting of a worm-wheel and worm, is 

 applied to an axle or barrel for raising weights, by a rope 3 inches in 

 circumference. The barrel or axle is 6 inches in diameter, the 

 worm-wheel is keyed on the barrel, and has 20 teeth, the worm is 

 single-threaded, and is moved by a handle 20 inches long, to which a 

 power of 50 lbs. is applied. 



Required the weight that can be raised by that power, the friction 

 being three-sevenths of the power ajiplied. 



11. A cheese-press has a screw 2 inches in diameter, the pitch of 

 which is 1 inch, and the screw is urged to rotate by means of a 

 lever, 5 feet long, with a power equal to 80 lbs. applied to the end of it. 



Required the pressure in lbs. on each square inch of the cheese, the 

 diameter of the cheese being 1 6 inches, and the friction of the press 

 being one-third of the power applied. 



12. A non-condensing steam-engine has a cylinder 10 inches in 

 diameter, the length of the stroke is 20 inches, and the number of 

 revolutions of the crank-shaft is 100 per minute. The pressure of 

 the steam in the cylinder is 3 Gibs, per square inch, and the resistance 

 caused by friction and back-pressm'e is 6 lbs. per square inch. 



Required the useful effect or force of the engine in horse-power, 



13. A steam-boiler, in which the thickness of the plates is three- 

 eighths of an inch, is 4 feet in diameter and the steam-pressure is 

 50 lbs. per square inch. 



Required the strain upon each inch in length, tending to rupture 

 the boiler. Find also the force in lbs. upon a transverse section of 

 1 inch in length of the boiler, having a tendency to burst it. 



14. A beam of Christiana timber, 10 inches deep and 14 inches 

 wide, is laid over a drain 12 feet wide, and found to carry 20,092 lbs. 

 when loaded in the middle. 



What load will another beam of similar timber carry, which is 

 14 inches deep and 10 inches wide, when laid over the 12-foot 

 drain ? 



