REVIEW QUESTIONS. 155 



3. (a.) Give the third law of motion and illustrate it. (6.) Give 

 the law of reflected motion. 



4. (a.) What would a 1470 Ib. ball weigh at 10,000 miles above 

 the earth ? (&.) Give the law that you use. 



5. (a.) How far will a body fall during the fourth second? (6.) 

 How far in four seconds ? (c.) What will be its final velocity ? 



6. The crank of an endless screw whose threads are an inch apart 

 describes a circuit of 72 inches. The screw acts on the toothed 

 edge of a wheel whose circumference is 90 inches and that of its axle 

 13 inches. On the axle is wound a cord which acts on a set of pul- 

 leys three in each block, the force of which pulleys is exerted on 

 the wheel of a wheel and axle, the wheel being 4 feet and the axle 

 8 inches in diameter. What weight on the axle will be lifted by a 

 power of 30 Ibs. at the crank, allowing for a loss of one -third by 

 friction ? 



7. (a.) What is the length of a pendulum making 25 vibrations a 

 minute ? (5.) How many vibrations are made per minute by a pen- 

 dulum 25 inches long? 



8. (a.) What is a horse-power ? (6.) A unit of work ? (c.) If a two 

 horse-power engine can just throw 1056 Ibs. of water to the top of a 

 steeple in 2 minutes, what is the height of the steeple ? 



9. (a.) What are the laws of machines? (&.) The facts concerning 

 friction? (c.) What is a lever? (d.) Figure a lever of each kind. 

 In a lever of the second kind the power is 4J-, the weight is 40 J, the 

 distance of the power from the weight is 18 in. (e.) What is the 

 length of the lever ? (/.) What the length of the short arm? 



10. If the diameters of the wheel and of the axle of a wheel and 

 axle are respectively 60 in. and 6 in., and the power is 150 Ibs., what 

 weight will be sustained ? 



11. (a.) Draw a system of 3 fixed and 2 movable pulleys. (&.) If 

 the power be 90 and the friction one-third, what weight can be 

 raised ? 



12. (a.) A weight of 12 pounds, hanging from one end of a five 

 foot lever considered as having no weight, balances a weight of 8 

 pounds at the other end. Find how far the fulcrum ought to be 

 moved for the weights to balance when each is increased by two 

 pounds. (&.) Give the law for the screw ? 



13. A capstan, 14 inches in diameter, has four levers each 7 feet 

 long. At the end of each lever a man is pushing with a force of 

 42 pounds. What is the effect produced, one-fourth of the energy 

 expended being lost by friction ? 



