L25 Feb OMG THAT GUY’S BEEN TO CERN SO JEALOUS >< SI Units P!"ti"e #$esti%n& Speed → v of ripples m/s 'e(en'ent %n& lambda → wavelength m gamma → surface tension kg/s2 rho → density kg/m3 g → gravitational acceleration m/s2 Usin) 'i*ensi%n!+ !n!+,sis- ./i"/ is t/e i)/t 0%*$+! 0% s(ee' %0 i((+es1 3 4 A6)!**!7/%8s#%%t67)!**!+!*b'!98 23 4 B6)!**!7/%8s#%%t6)7+!*b'!8 93 4 Cs#%%t6)!**!7+!*b'!/%8 Ans& 9 % % !((!ent+, e4en i0 it’s n%t *!t/e*!ti"!++, i)/t it’s %:!, "$; .e’e (/,si"ists333 b$t I’* *!t/ RAs%333 3 C%nst!nts& s(ee' %0 +i)/t " *7s B%+t;*!nn "%nst!nt : % : B J7= P+!n":’s "%nst!nt / Js % e'$"e' "%nst!nt / /72(i e+e*ent!, "/!)e e C A4%)!'%’s n$*be N A 7*%+ G!4it!ti%n!+ "%nst!nt G N*2:/2- n%t e#$!+ t% )!4it!ti%n!+ !""e+e!ti%n P!"ti"e #$esti%n& sigma → Stefan-Boltzmann Stefan-Boltzmann constant /m2!" H%. t% e?(ess in te*s %0 t/e !b%4e 0$n'!*ent!+ "%nst!nts1 @ :)*2s9 N :)*s2 J :)*2s2 C As Ans& A:7"2/9A:7"2/9- ./ee ./ee A is ! 'i*ensi%n+ess 'i*ensi%n+ess "%nst!nt "%nst!nt
Un"et!int,
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uncertainties arise from errors made in measurements# systematic or random$ systematic → can be eliminated eg$ zero error# random → unpredictable# cannot be eliminated but can be reduced statistically$ only way to get rid of random error as much as possible is to make lots of measurements and take the average# which minimises the uncertainty to an e%tent P!"ti"e #$esti%n& (ei%' %0 si*(+e (en'$+$* T T 2(i s#%%t 6+7)8 + +en)t/ %0 (en'$+$* ) )!4it!ti%n!+ !""e+e!ti%n- 3D *7s2 'e+t! T %4e T- 0!"ti%n!+ $n"et!int, 7 ? 'e+t! + %4e + 7 , Ans& 0ist- *!:e ) t/e s$be"t ) 62(i7T82+ 2(i /!s n% $n"et!int, s% 'e+t! ) %4e ) s6'e+t! T %4e T8 6'e+t! + %4e +8 'e+t! ) 7 3D 62? ,8 'e+t! 6 %4e T8 %4e 6 %4e T8 'e+t! %4e 'e+t! T %4e T /!s n% $n"et!int, s% 'e+t! %4e is 'e+t! 6 %4e T8 %4e 6 %4e T8 'e+t! T %4e T
P/,si"s %0 M%ti%n vector → scales that have both magnitude and direction result of two vectors → draw parallelogram or head to tail free body diagram b$t *!, n%t be !b+e t% '!. !++ t/e ti*e resolving vectors → draw the vector from the origin on a &artesian plane# and
e%press it as the result of two vectors on the % and y a%is# at right angles to each other# then use trigonometry and pythagoras's theorem to (nd angle and magnitude +et be t/e *!)nit$'e %0 t/e 4e"t% !t !n)+e teet! t% t/e ?!?is +et ? be t/e 4e"t% %n t/e ? !?is- , be t/e 4e"t% %n t/e , !?is ? "%s teet! e#$!ti%ns %0 "%nst!nt !""e+e!ti%n ! /tt(&77(/,si"s3b$3e'$7e'ne72s(7"+!ss7e#$!ti%ns3/t*+ 4 $ !t s 35 6$ 48 t s $t 35!t2 42 $2 2!s 0%"es → conservative# results in no change in energy if the energy is moved from one to another point and back → non-conservative# dissipative# eg$ friction# air resistance# if an ob)ect is moved in air to another point and back to the original point# some energy is already lost to overcome air resistance ne.t%n’s 9 +!. st- NL& *%ti%n %0 ! b%', is n%t !""e+e!te' in !bsen"e %0 !n %$tsi'e 0%"e 2n'- N2L& F *! 9'3 N9L& e4e, 0%"e /!s !n e#$!+ !n' %((%site e!"ti%n N2L& F *! ( *4- ( *%*ent$* t%t!+ *%*ent$* %0 ! "+%se' s,ste* is "%nst!nt- n% %$tsi'e 0%"es !00e"tin) ( !n' 4 !e 4e"t%s "%e00i"ient %0 st!ti" 0i"ti%n is $s$!++, +!)e t/!n "%e00i"ient %0 :ineti" 0i"ti%n @ Fs J%$+e .%: '%ne %n ! b%', *%4e' t/%$)/ * $n'e 0%"e %0 N work done is the mechanical transfer of energy → something must be moving# )ust energy transfer doesn't count t,(es %0 ene), → gravitational potential energy mgh → radiated energy# like electromagnetic waves → elastic potential energy *$+k%2# a spring has the potential to do work when eg$ compressed → kinetic energy *$+mv2
→ internal energy of ideal gas power → speci(c de(nition# rate of work# work done over time taken# att , /s e.ciency → rate of useless work done over rate of energy consumed , work done over energy e%panded
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