AGE OF MACHINERY 503 



5. If you were pulling 50 pounds on the end of a rope with 4 

 pulleys, about how heavy a boat could you pull ashore? 



6. The circumference of a wheel on a letter press is 30 inches, 

 the pitch of the screw is J inch; if the force is exerted on the wheel, 

 with what pressure would letters be pressed together in the letter 

 press? 



7. A person weighing 150 pounds walks upstairs to a height of 15 

 feet. How much work did the person do? 



8. How much work would be required for you to walk upstairs 

 in your home? 



9. What horse power of work would be accomplished if it took 

 you 5 seconds to go upstairs? 



10. How much work would a horse do if he pulls on a load with 

 a force of 100 pounds and travels 5 miles? 



11. A man is shoveling coal into a furnace. Each time he lifts 

 a shovelful of coal, he carries 10 pounds of coal from the floor to 

 the furnace door, a distance of 2 feet. How much work does he 

 do to accomplish this, if he puts 5 shovelfuls of coal in the furnace? 



12. Why is it easier to push a barrel of molasses up an inclined 

 plane (plank) into a truck than to lift it directly up? 



13. Why are machines oiled? 



14. Why do some machines have ball bearings? 



15. Name some machines which use ball bearings. 



16. Why does a clock need oiling? 



17. Why does it not keep good time if it has not been oiled for 

 some time? 



18. What is a " hot box "? 



19. What is the result of friction? 



20. What mechanical advantage has a sewing machine, a bread 

 mixer, a meat grinder, fire tongs, vacuum sweeper, door knob, oars 

 in a rowboat? 



21. Name some machines you have at home and tell their 

 mechanical advantage. 



22. How much should a horse pull if he weighs 1000 pounds, 

 1600 pounds, 2000 pounds? 



23. What horse power would these horses exert doing work at 

 the rate of 2J miles per hour? 



