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Chapter5 - Chapterfi A force is a push er a puiir it is...

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Unformatted text preview: Chapterfi A force is a push er a puiir it is that which causes an chject tn acceierate. The unit cf force in the metric system is the Newtcn. Puree is a vector quantim Every bcdy centinues in its state nf rest er cf uniferm mntinn in a straight iine unless it is cempeiieei by a fume tn change that state. The mass of an abject is that nrnperty that specifies hcw much resistance the Object exhibits to changes in its veiccity (a measure cf the inertia ef the ehject). Mass is a scaiar anantity, The unit cf mass in the metric systcrn is the kiicgrarn. The net three 2? acting an an chjcct cf mass “in” is cqnai tc the prcauct ni the chi cctfis mass with its acceieraticn ii. Read sections 13.1 and i339 Net’s Lew Grmiizee: Every particic (with ncnmzcrn mass) in the universe attracts every ether particic {with itch- zcm mass) with a three that is directiy prepcrticnai tn the prcanct of their masses ma inversely prcpcrtienai t0 the square cf the distance between them That isg I??? nun2 b" i?! Z G 1.2 6/733; Where G * 6.67Xm'“ NtrtZ/kg2 at» the universal gravitaticnal cchstaht. r = distance from the center cf mass cf che particle tn the center cf mass cf the ether particle. The attractive three exerted hy the Earth ch an ehject is called the gravitationalfcrcc Pg. This three is called the weight ct” the cbj ect, and its directicn is tc‘ward the center cf the Earth. The weight of an abject of mass m on the Earth has a magnitude equal tc; Mfim R 2 E gr g £26 The quantity G R: appears sc eften that it is given the name igi cr simply g. This quantity is alsc called the gravitaticrzaifieid generated by the Earth at lccaticns near its sarface. The gravitatienai fiein g is a reefer quantity with a direerian teward the center at the Earth? and with a magnitude nefmeé as M W: 26% is s R2 E nsing G : same“ NmZ/kg2 ME m 5698x1024 kg (mass nf the Earth) RE : 6.37Xmé m (radius efthe Earth) yieins a Value 0f g x 9.8 m/sZ. One can thus say that the weight ef an abject ef mass m en the surface nf the Earth is Egmrng Where g x the aeeeieratien dine tn gravity? aiways direeted inward the center ef the Earth. New yen knew Where the 9.8 W32 mines frnnm H bedy “A” exerts a farce EB err hody “B”? thee hedy “B” exerts arr equal: (magnitude) am eppesite (directien) farce EA err bedy “A”. FAB : FBA Forces always occur in pairs. Censider a Meek of mass m sliding with a speed v en a horizemsj surface. Let F he the net force exertee by the herizerltai surfaee err the Neck. The hernia! tersea n9 is (lefineu as the eemnenent ef the force F? that is nemenrtie‘ular (er normal) tn the herizental surface. Theflicz‘iunal forcefis the cempenent 0f the force F' that is parallel to the hurizontal surface. The are twe “kinds” of frictional fumes: {A} The Kinetie Frictiuual Furcefi (sliding) The magnitude 0f the frietiunal farce fl: is prepartional tn the magnitude ef the nermal a farce. The eenstant 0f prepertienallty is human as the mefficiem usz’neticflictien ukt fix ttktt {AhWAY31 : The Statie Frietienal Fereefs the slipging) The magnituue uf the frictienal three f; is relateu tn the magnitude 0f the neaal three it. fifiwn its = the eeeffieient of static frietiens The equaiity Sign hams when the surfaces are an the verge 9f siipping (impending mntien). The inequality Sign heids when the surfaces are net en the verge ef siipping. Objeets in Enniiihriunt: An object is said to he in mechanical eqniiihrium when twe canni‘tions are met: {a} The netfnree aeting an it is eqnai tn zeree This ensures transfaztenai enaitz’hriam. Frern 2? n ma we see that if 2F 2 Q 3 then name ::.> t{Exemistant That is, the abject is (i) at rest and stays at rest er (ii) the ehj eet meves in a straight Tine with eenstant veieeityi {h} The net terque aetihg es the ehjeet is zete. This ehsui‘es rammed eqmiz’brmm, Mere eh this tepie when yth study ehaptet’ m (in Physics 7B). Strategy fer appiying Newmn’s ans sf metiem (a) iseiate (eensider) s pert ef the system or the entire system and draw the threes acting ON its (b) Apply Newmh’s 2rid iaw 0f metien in eempenem fem; (e) Ssh/e fee shy uttkfiQth quantities {d} if the seeeierstieh ef the ehj eet is CfiflSiai‘iig then. we may sppiy the hinemstie equetiehs. New we are ready te d0 ists sf examples. ,. ...
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