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8/20/2019 Est Fin 2014sol
1/2
L E E = L dI dt I = E t/L I 0 = E τ L/L
τ L = LI 0/E . I 0 L
R L R L/R τ K
I 0 V max = RI 0 V max V 0
L dI dt = RI = Rdqdt
q
I 0 0 LI 0 = R∆q
∆q = I 0L/R V 0 A = V 0∆q
P = Aτ L
= V 0I 0L
Rτ L= V
0E R
.
RC
K 1 LC
T LC = 2π√
LC RC T LC
V 0 V max i LC i = I 0 i = 0 LC
1
2LI 20
τ L
Q = V 2
avτ L/R
V 2avτ LR
= 1
2LI 20 ⇒ V av = I 0
LR
2τ L=
E I 0R
2 .
q C = τ LV av/R RC τ LC
∆V = q C /C = τ LV av/(RC )
U 0 = ∆ V
2 =
τ LV av
2RC =
I 0L
2C I 0
2RE .
E = − GMm2a
M m a a
2a = RE + rS RE rS
RE /2 23/2
T t t = 2−5/2T ≈ 64.6 days
v0 = 29.8 km/s vS
−GMm2a
= − GMmRE + rS
= −GMmRe
+ mv2S
2 ,
vS =
GM
RE
2rSRE + rS
.
v20 = GM
RE
vS = v0
2rS
RE + rS= v0
2sin
α
2
≈ v0
√ α.
vS ≈ 2.8 km/s vE = v0−vS ≈27.0 km/s
∆Π = GM EmR
= gmR
gR + v2E2
= u2
2 M E
u
u =
v2E + 2gR ≈ 29.2 km/s.
mg
T
F
T mg
−(x/l)mg l x = 1cm
F = F
− (x/l)mg F = 0 ∆x
∆F = ∆F
− ∆xl
mg
F
= kd−n k
∆F
= F
(d)∆d = kn
dn+1∆x,
∆d = −∆x ∆F =
kn
dn+1 − mg
l
∆x.
∆F = 0 n k
k
dn − xmg
l = 0 ,
kn
dn+1 − mg
l = 0;
k
dn =
xmg
l ,
kn
dn+1 =
mg
l .
d/n = x
n = d/x = 4.
v0 = v k vk (k + 1)
v
u = vk−fv1+f
vk+1 =v + 2 vk−fv
1+f = 2
1+f vk + 1−f 1+f v v0 = v
v1 = 3−f 1+f v =
4
1+f − 1
v
n vn =
2 2
1+f
n − 1 v
v2 = 2gh0 v2n = 2ghn
hn/h0 =
vn/v0 =
2
2
1 + f
n− 1.
f = 0.5 n = 10
940nm 620nm 590nm
525nm
470nm
450nm
I
R
8/20/2019 Est Fin 2014sol
2/2
V d = E − IR
E p E p =hc/(λe) IR = E − V d IR 1/λ
IR = E − 1λ
hc
e .
A = hc/e h =eA/c
A
A ∆A = 1
2(Amax − Amin ) ∆h = h∆A/A
vx − vy A (0, v) B (v, 0) vx − vy
µg v
√ 2
t = v√
2/µg ≈ 7.2 s
p↑ =A · e−m A
A ·e−/2 + A · e/2 = 1
A = 1
e−/2kT + e/2kT =
1
2 cosh(/2kT ).
p↑ = e−/2kT
e−/2kT + e/2kT .
E = N
2
e−/2kT − e/2kT e−/2kT + e/2kT
= −N2
tanh(/2kT ).
E ≈ −N2/4kT
C = dEdT = N 2/4kT 2
y α = y/L
∆ = 2l cos α ≈ 2Nλ − N λα2
ϕ = 2π∆/λ = 4πN − π(2Nα2 − 1) 2π(2N − n) n
α =
n + 0.5
N ⇒ yn = L
n + 0.5
N ,
n = 0, 1, . . . N n x
n
√ 1 = 1
√ 3 ≈ 1.73√
5 ≈ 2.23
ϕmax = 4πN + π ϕmin = π
m = (ϕmax − ϕmin )/2π = 2N.
dq = C vdT T = 0
q = T 0 C vdT q ≈ R·560J/K ν = a3ρ/M A ≈ 0.117mol Q = qν ≈ 546J ν E = hν p = h/λ = hν/c = E/c α
p = E
c cos α
p ∼ Ec
cos α
¯ p = Ec
1
2π
cos
2 αdΩ
dΩ = 2π sin αdα ¯ p =
Ec π/20 sin α cos2 αdα = Ec π/20 cos2 αd cos α = E3c
1/c Q/c a3ρv ∼ Q/c
v ∼ Qρa3c
≈ 0.67mm/s.
1
3
v ≈ 0.22mm/s
AT 3dT = −σST 4dt A σ S
dT
T
=
−Bt
⇒T = A
·e−Bt.
1/vT
vT = RT/M H
a3ρv ∼ Q/vT
v ∼ Qρa3
M H RT
≈ 180m/s.
T 4
a n n = 10
nλ/d = a/L L d
d = nLλ/a.
b
ε = b − b0
b0,
b0
σ = 4 Nmg
πd2 ,
N m
∆ε = ε∆b
2
b − b0 + 1
b0
,
∆b ≈ 0.5 mm
∆σ = 2σ∆d
d .
ε = ε∗ ε1 > ε∗
ε1 < ε∗