Analysis of a course of lectures on natural and experimental philosophy. Viz. 1. Magnetism, 2. Mechanics, 3. Chemistry, 4 & 5. Pneumatics, 6. Hydrostatics, 7. Electricity, 8. Fortification, 9. Optics, 10. Use of the globes, & c. 11 and 12. Astronomy / by A. Walker.

  • Walker, A. (Adam), 1730 or 1731-1821.
Date:
[1790]
Catalogue details

Licence: Public Domain Mark

Credit: Analysis of a course of lectures on natural and experimental philosophy. Viz. 1. Magnetism, 2. Mechanics, 3. Chemistry, 4 & 5. Pneumatics, 6. Hydrostatics, 7. Electricity, 8. Fortification, 9. Optics, 10. Use of the globes, & c. 11 and 12. Astronomy / by A. Walker. Source: Wellcome Collection.

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    C *7 ] The inclined plane is half a wedge, and therefore its power is, as its length is to its height ; i. e. I fhall roll a cylinder up an inclined road of twenty yards in length, and but one yard perpendicular height, with one twentieth part of the force that would be neceffary to lift it perpen¬ dicularly that yard. The fcrew may be confidered as an inclined plane wrapt round a cylinder ; therefore as the power moves round the cylinder; while the weight rifes, the power has an advantage over the weight, as the length of one thread round the cylinder, is to the distance of one thread front another ; or as the velocity of the power is to the velo¬ city of the weighti In a common jack We have all thefe powers together, if to an arm of the fly the power be applied ; and fo far as that power moves farther than the weight, fo much is the advantage which the power has over the weight. If machines could be made to move without friction, the lead degree of power added to that which balances the weight would be fufficient to raife it : But as the fmooth- eft bodies are full of pores, and little eminences, thefe will lock into one another in rubbing bodies, and greatly re¬ tard the motion of a machine. The fridtion in the lever* and in the wheel and axle* is very fmall : In pullies it is very confiderable : But in the inclined plane, the wedge, and the fcrew* it is very great. The allowance made for friction in machines confiding of feveral of the mechanic powers, is ufually one third; i. e. after calculating all the fmgle powers as above, and multiplying thefe into one another, from the 1 aft product I deduct one third of it, and the remainder is the true momentum or force of the machine. Friction is of two kinds: The rubbing ftic- tion} and the friftion by contacl j the rubbing of the locked D wheel