Lecture No: 66
Physics
FIGURfi 3.1
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' OYNAJńICS - ł
There aremanydifferent crpes offoxes u us, I>zt physicists haxectassifled forcesIntoonly
ft cetegories besedali hewobjectsInteract withoneanoclser. The four fw›dernentat forces of
nature are thepartIat\onat force, thee xtromapatic ferce, thestrong full Fforce, and1e
weak nuclear feroe. Physicists haye dasslfled att forces that exlsta one of these four
f axJarnental feroes. Physicists explain them f\«slamental forces through exchange p a r t l y
Elementary pa•tictm, much less m o v e than a proton, travel from
object to arother
“canylng" the force. In thus way, each force \a ‘earned' or mediated by the exclmnge of a
. Strong Nuclear Fox›e•. the atro ucle fbrc 1 Lhesbongestof allele hadarnenfal forces.
It keeps the positively oiarged protons tightly Pe ed in the n‹<teus of an atom, by ‹•rercon›ing
the repulsion beMeen them . Tbe exchange particles ofstrand foroe are called pions, with other
heavyparttc&. The stnxyn
forcehma verys h o r t s , neartyequaltothedlameterofa
ectrtanaqnetlcFlea: Theelect
c
e l e c t s . I t \rx:fudes
both ete
forces ard
tk f‹x<es. The electro‹rng/wtIc fbrce can exert e4¢her an
attractonor arepulstm, soon average, lie forcestend torara•at eachother out andItseftéctIe
not observed. The etectromagneLc force Tsmed1ated by a massless pa•tfde gnown asa ptoton.
Themasstess nature of thephoton makestheeffechverangeinFaete, even thoughthestrength of
the forco decreases rapidly as the distance between the objects incroazes. The narmal force,
fricnon, and tendon are ca‹ned by the \nteracuo› or particles on the contact surraoes ard are
tlntaa
cé'theeIectromagne¢icforce.
. WayItat1 at Fcax›e: T h e y , o r the force of pavity, is the f o r c e p “w
between all a
. Gravt
r the weakest ef the four fundamental forces
(with least relatNe suength), thefsrceof gray\ty between twooQects Is no0t@lump If at least
one of theob}ectshma large mass such as ctars, planets, andmoons. It folds them together and
controls tfieirn¥zttons1nthesamewayrhat Itcontrols zbarnotionoffau\ngobjects heMon Earth.
Crasftatiovl foroe is theorized to be an escharye force wfth a massages mediating jmrticle
’$ra
*. The massfessnatzaeof fhe$zavitonaflowsgravltytohave tnfinfreran$edmtlar to the
e
c force.However, thegmvltonfs theonlyexchangeparticter›otdetectedyet.
. WaaL Iguclaar force: The weaL nuclear far is very weak, 10 /X0 times weaker Item the
strong nuclear force and has W shortest rangeof any of the fundamental foroes. Omplte tfrls,
w#bknuclParfor plays amaj€¥*r¥Ig0In tkPst
uFebf unJvPLse. ItScan A n g e l l
mediated by the exchmge of threediffers
lied
. Theweagjjggtear
theweak foroechangesthefl
of an elementary particle cal ›da q‹nr Whm this process eccurs, a neutron
tI r g a m a r o
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