--????B: ???

1
??????????--?????(2005)???(???101?)???????
?????100-400 (???)??? ???019????
????????(????)???? ???????????? ??
2
2/26 (???019?) --????3 ?? (????5)
--????B ??? --????4 ?? (????6) --????5
???? (????9) 3/12 ??3 (??)(??????) 4/09 ??4
(??)(??????) 5/14 ??5 (??)(??????)
3
????? ??? 1.?? 2.????????(lt2?/????)???????
3.????(???????????) ??? 1.???? 2.???? 3.?????????
???? ??? 1.???? 2.????????
4
??3 ?? (????5)
?? ??????(one dimensional collision)????????? ??
?? p mv, ??(E) ??(K) ??(U) ??(?Q) ??
?????????, ???, ???? ?????II ??1 ??(m1)
?????(v1i) ?????(v1f) ??2 ??(m2 ?
m1)(???) ?????(v2i 0/??)
?????(v2f) ??????, ? ????? pi pf (i
initial, f final) kg.m/s
m1v1i m1v1f m2v2f (v2i 0) (3-1)
5
????? Ei Ef J kg.m2/s2 ???????
???????? Ui Uf (????) ????????
??????????(????????Q) ??????(???) Ei Ki
m1v1i2/2 (v2i 0) ?????? Ef Kf ?Q
m1v1f2/2 m2v2f2/2 ?Q 1. ????(elastic
collision)(?????Q0) ?????????????????????,
????, ???? ????? ???? m1v1i m1v1f
m2v2f (??) ???? m1v1i2/2 m1v1f2/2
m2v2f2/2 (????) (3-2)
6
??(m1 lt m2 or m1 gt m2) ???? ??(??) ?????
2. ?????(inelastic collision)(??????Q)
??????????????????, ??????????, ? ???????
???? m1v1i MVf (M m1 m2, Vf v1f
v2f ) ???? m1v1i2/2 MVf2/2 ?Q (?????,
??????) (3-3)
7
???B ???(Angular Momentum)(19)

• ????(plenary motion)
• ???(N. Coperrnicus)(1473-1543)????
• ???(J. Kepler)(1571-1630)??--??????(Keplers
  laws)
• ??????? ???????
• (?) ???(solar system)??
• (?) ??(galaxy)??
• (?) ??(hurricane)/??(typhoon)??
• (?) ?????(whirlpool)??
• ????(conservation of momentum)
• ? F ma mdv/dt dp/dt (?? p ? mv)
• If F 0, then p constant (????)
• ?????(conservation of angular momentum)
• ?? t r x F r x (dp/dt) d(r x p)/dt dL/dt
  (??? L ? r x p)
• If t rFsinq 0 r 0, F 0, or q 0 (R //
  F)
• then L constant (?????)

8
??4 ?? (????6)
?? ???????????????(rotation)???????? ??
??????(rotational axis)?? ???(angular
displacement) q rad 360o 2p radians
???(angular velocity) w dq/dt
rad/s ????(angular acceleration) a
dw/dt d2q/dt 2


rad/s2 ????(torque) t
r x F (F ??, r ???????) m.N ?
a ? t or t Ia
???? ?????????(rotational inertia)
I kg.m2 I Si miri2 (mi ??,
ri ???????) ? rr2dV (r
??????, r ?????, dV ????) ??t
constant, ???????(a constant) ??t
0, ??????(w constant) (4-1)
9
(?) ????(rigid body)?????(??M, ??R)
I MR2/2 (??????????????) I
MR2/2 Mh2 (?????????h????) ??
???? ??????????????(???????)?? (?????/???????, I
? MR2/2) ??(???????)?????, ?????????m ??(???????
)??????z?/????/????? t r x T Ia (r
r1 I cm or r2 2 cm, T ?????) T Ia/r
r x T rTsinq z rT z, if q 90o
????(????, ????)??-z? Fnet mg - T ma
mra (a ra) ???????z? a mgr/(I
mr2) ????????f (4-2)
10
(4-3) ????? ???? ????
11

• ?? ???????
• ???? ??????????
• A. ??????
• ??????(r1 or r2)?????(m1, m2 or m3)
• ???q(??) 1/4, 1/2, 1, 3/2, (1 ? 2p
  rad)
• ????t (s) t 1, t 2, t 3, t4,
• ???w(rad/s) w1, w2, w3, w4, (???)
• ????a ????????
• ?? q(t 2) ???????(q at 2/2)
• w(t) ???????(w at)
• ???????(r1, r2)?????(m1, m2, m3)?????
• (a1, a2, a3, a4, a5, a6)
• ?????
• t rT r(mg ma) rmg (if a ltlt g)
• (t1, t2, t3, t4, t5, t6)
• (4-4)

12

• ???I?
• ?? t(a) ???????(t Ia), ??I
• ????????I 13.3 g/m2 ??
• B. ??t Ia
• ????r?????m??
• t rF rmg constant (????)
• ??????(???)I?, ???????
• ???????(?,?)?????? h1, h2
• ???(??mc, ??ri, ??ro)????(?????, ????)
• ??????
• Ic Icm mch2 mc(ro2-ri2)/2 mch2
  (x2, ?????)
• ????? Itotal I 2Ic
• ???????(h1, h2)??????(mc1, mc2)?????a
• Itotal a t rmg? ?????
• (4-5)

13

• C. ?????????
• ????????, ???m???h???????, ???
• ????(??r)
• ?????t 0 (a 0), ??????????(w)??
• w2 w02 2aqt (w0 0, ???? qt
  h/r (rad))
• or a w2r/2h
• ???????????(f)
• ???(T)
• w 2pf 2p/T
• ???????a ?A??
• D. ????
• ????,
• ?? ???? ????
• mgh Iw2/2 mv 2/2
• (??v wr)

14
??5 ???? (????9)

• ?? ?????????????????(simple harmonic motion)
• ?? ??????(x)??, ???????(Hooks law)
• ??? Fr -kxx (k ????/spring
  constant, x ? x/x)
• ???? U kx2/2
• ?????ms 0 (ms ltlt ????m)
• md2x/dt 2 -kx (???????)
• (?) x(t) A sin(k/m)1/2t f A
  sinwt f
• ??(amplitude) A
• ???(angular frequency)
• w ? 2pf ?(k/m) rad/s
• ??(period) T ? 1/f ? 2p/w
• ??(phase) f
• ?????ms ? 0
• w k/(m ms/3)1/2
• (5-1)

15
?? ??????????????? ?????III 1. ????????k
A ??(static)?? ?????(m1)????,
???, ???y1 ?? F F1 Fr m1g - ky1
0 k(static) m1g/y1
(?????????) B ??(dynamic)??
?????(m1)????, ??y2?????(??A y2-y1)
?? T 2p?(m1/k)
k(dynamic) 4p2 m1/T2
(???????) (ms???)
(5-2)
16
2. ????(coupled oscillation) ????
??(m)????????(k1,ms1)(k2,ms2)????
???????????????, ???(???, ????) md2x/dt
2 - k1x - k2x -(k1 k2)x ?????? k
k1 k2 ?????? U (k1 k2)x2/2
A. ??????(???)m ???T?m???
B. ???/??????k ?T?k??? C. ????A
?T?A??? D. ???v(t)???x(t)???
E mv 2/2 kx 2/2 constant
(??????) (5-3)