REVIEW. 115 



REVIEW QUESTIONS AND EXERCISES. 



I. (a.} What is a machine ? (6.) What is a machine good for ? 

 (c.) State the general laws of machines and f (d) illustrate by the 

 pulley ^&<M<&'tc^ 



i 2. (a.) What are the arms of a lever ? (6.) What is meant by the 

 moment of a force ? (c.) Illustrate the equality of moments in ma- 

 chines by the wheel and axle. 



3. (a.) What are the respective advantages to be gained by the 

 several classes of levers? J (&.) Explain the advantage gained .by a 

 claw hammer in drawing a nail, (c.) What is meant by double 

 weighing ? 



4. With a lever of given length, in which class will a given 

 power yield the greatest intensity of effect ? 



5. (a.) To what kind of a lever is ordinary clock-work analogous? 

 (&.) Show why. 



6. (a.) Does it require more work to lift a barrel of flour into a 

 wagon four feet high than to place it there by rolling it up a plank 

 12 feet long ? (6.) Show why. 



7. (a.) Give the static law for the inclined plane when the power 

 acts parallel to the plane. (&.) When it acts parallel to the horizon, 

 (c.) Figure a system of pulleys by means of which a weight of 5 

 pounds will support a weight of 25 pounds. 



8. (.) Figure a system of 4 movable pulleys by means of which. 

 a weight of 3 Ibs. will support a weight of 27 Ibs. (&.) Deduce 

 the formula for the screw from one of the general laws of machines. 



9. (a.) In raising a boy from a deep well by means of a common 

 rope and pulley, what disadvantages arise from friction ? (6.) What 

 immense advantage ? 



10. (a.) Explain the cause of friction. (&.) Why is friction between 

 iron and iron greater than that between iron and brass? 



II. (a.) How may the centre of gravity of a ring be determined ? 

 (&.) What is the value in inches of the metric unit of length? 



12. A body moving with an energy of 20 foot-pounds, strikes the 

 end of the arm of a lever of the first class, four feet from the 

 fulcrum, (a.) How many foot-pounds will be exerted by the other 

 end of the lever, 6 feet from the fulcrum ? (&.) How far would it 

 raise a weight of 4 pounds ? 



13. Deduce the static law for the inclined plane, first case, by 

 resolution of the force of gravity. 



14. (a.) What force is necessary to overturn a body ? (&.) What 

 difference between the forces producing uniform and accelerated 

 velocities? (c.) Show that the screw is a modified inclined plane. 



