# Example 19-1
w = 500 kcal * 4.186e3 J/kcal
m1 = 60 kg
h = w / m1 / grav()

# Example 19-2
m1 = 20 kg
c = 450 J/ kg degC
delt = 80 degCdiff
q1 = m1 * c * delt
c2 = 4186 J / kg degC
q2 = m1 * c2 * delt

# Example 19-3
MKS(degC)
vol = 200 cm^3
t_tea = 95 degC
m_cup = 150 g
t_cup = 25 degC
rho = 1000 kg/m^3
m_tea = rho * vol
c_tea = 4189 J/kg degC
c_cup = 840 J/kg degC
BEGIN
  t_final = 95 degC
  eq1 = m_tea * c_tea * (t_tea - t_final) - m_cup * c_cup * (t_final - t_cup)
END
solve(eq1, t_final)

# Example 19-4
MKS(degC, J / kg degC)
ma = 0.159 kg
ta = 540 degC
mw = 0.4 kg
tw = 10 degC
mc = 0.2 kg
tf = 30.5 degC
cw = 4189 J/ kg degC
ccc = 900 J / kg degC
BEGIN
ca = 100 J / kg degC # initial guess
eq1 = ma * ca * (ta - tf) - mw * cw * (tf - tw) - mc * ccc * (tf - tw)
END
solve(eq1, ca)

# Example 19-5
MKS(degC, J / kg degC)
m_i = 0.5 kg
t_i = -10 degC
m_w = 3 kg
t_w = 20 degC
c_w = 4189 J/ kg degC
c_i = 2100 J / kg degC
lf = 333 kJ/kg
e_melt = m_i * lf
BEGIN
tf = 1 degC
eq1 = m_i * c_i * (0 degC - t_i) + e_melt + m_i * c_w * (tf - 0 degC) - m_w * c_w * (t_w - tf)
END
solve(eq1, tf)

# Example 19-6
MKS(degC, J / kg degC)
chg = 140 J / kg / degC
mhg = 1 kg
t_melt = -39 degC
ma = 0.5 kg
mw = 1.2 kg
tw = 20 degC
tf = 16.5 degC
chg = 140 J / kg / degC
ca = 900 J / kg / degC
cw = 4186 J / kg / degC
qhg = mhg * chg * (tf - t_melt)
qa = ma * ca * (tw - tf)
qw = mw * cw * (tw - tf)
BEGIN
lhg = 1000 J / kg
eq1 = mhg * lhg + qhg - qa - qw
END
solve(eq1, lhg)

# Example 19-7
MKS(J)
heat = 2500 J
work = 1800 J
del_e = heat + work

# Example 19-8
MKS(J)
m1 = 3 g
v1 = 400 m/s
v2 = 200 m/s
dele = 0.5 * m1 * ( v1^2 - v2^2)

# Example 19-10
MKS(J)
p1 = 2 atm
vol1 = 8 L
w1 = p1 * vol1

# Example 19-11
MKS(J)
n1 = 0.25 mol
tf = 400 degK
ti = 1150 degK
dele = 1.5 * n1 * gas() * (tf - ti)

# Example 19-12
MKS(kJ)
pa = 100 kPa
va = 1 m^3
ta = 300 degK
pb = 200 kPa
vc = 0.5 m^3
gam = 5/3
vb = va * (pa / pb)^(1/gam)
wab = -pa * va^gam * (1 / (1 - gam)) * (vb^(1-gam) - va^(1-gam))
wbc = -pb * vb * ln(vc / vb)

# Example 19-13
MKS(J/s)
a = 2 m * 1.5 m
h = 3.2 mm
t1 = 1 degCdiff
k = 0.84 J / s m degC
dqdt = k * a * t1 / h

# Example 19-14
MKS(W)
t1 = 15 degC
t2 = 34 degC
eps = 0.7
sig = 5.67e-8 W/m^2 degK^4
a = 1.5m^2
dqdt = eps * sig * a * (t2^4 - t1^4)

# Example 19-15
ts_over_tb = 2
qb_over_qs = 10^4
rs = 7e8 m
rb = sqrt(rs^2 * qb_over_qs * ts_over_tb^4)

# Homework Problems:

TBD