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{
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{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Chapter 5: Surface Tension"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Exa 5.1"
]
},
{
"cell_type": "code",
"execution_count": 1,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Work (dyn cm or erg) = 5.03e+04\n",
"press enter key to exit\n"
]
},
{
"data": {
"text/plain": [
"''"
]
},
"execution_count": 1,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"#If the surface tension of a soap bubble is 0.4 N/m, what work is required to\n",
"#increase the diameter from 5 to 15 cm?\n",
"import math\n",
"#initialisation of variables\n",
"St= 0.04 \t\t\t\t\t\t\t\t\t\t\t\t\t\t\t#N/m\n",
"d1= 5. \t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t#cm\n",
"d2= 15. \t\t\t\t\t\t\t\t\t\t\t\t\t\t\t#cm\n",
"#CALCULATIONS\n",
"W= St*1000.*2*4*math.pi*(math.pow((d2/2),2)-math.pow((d1/2),2))\t\t#Work\n",
"#RESULTS\n",
"print '%s %.2e' % ('Work (dyn cm or erg) = ',W)\n",
"raw_input('press enter key to exit')"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Exa 5.2"
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Presuure difference (lbf/ft^2) = 14.12\n",
"press enter key to exit\n"
]
},
{
"data": {
"text/plain": [
"''"
]
},
"execution_count": 2,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"#By much does the pressure inside a 0.017 in droplet of water at 20C\n",
"#exceed the outside pressure.\n",
"import math\n",
"#initialisation of variables\n",
"R= 0.017 \t\t\t\t\t\t\t\t\t\t\t\t#in\n",
"sigma= 72.8 \t\t\t\t\t\t\t\t\t\t\t#m N/m\n",
"#CALCULATIONS\n",
"P= (2*sigma*0.005*0.017)/(72.8*R*7.08*math.pow(10,-4))\t#Presuure difference\n",
"#RESULTS\n",
"print '%s %.2f' % ('Presuure difference (lbf/ft^2) = ',P)\n",
"raw_input('press enter key to exit')"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Exa 5.3"
]
},
{
"cell_type": "code",
"execution_count": 3,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
" Difference in mercury level (cm (depression)) = -2.48\n",
"press enter key to exit\n"
]
},
{
"data": {
"text/plain": [
"''"
]
},
"execution_count": 3,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"#A 0.4 mm diameter glass tube stands vertically in a dish of mercury at 20C.\n",
"#Determine the difference between the level of mercury in the dish and in\n",
"#the tube. The specific gravity for mercury is 13.6 and the contact angle \n",
"#with glass is 130C\n",
"import math\n",
"#initialisation of variables\n",
"d= 13.6 \t\t\t\t\t\t\t#gm/cm^3\n",
"g= 980 \t\t\t\t\t\t\t\t#cm/s^2\n",
"D= 0.4 \t\t\t\t\t\t\t\t#mm\n",
"angle= 130*math.pi/180. \t\t\t#radians\n",
"s= 514. \t\t\t\t\t\t\t#dyn/cm\n",
"#CALCULATIONS\n",
"h= (4*s*10*math.cos(angle))/(d*g*D)\t#Depression in mercury level\n",
"#RESULTS\n",
"print '%s %.2f' % (' Difference in mercury level (cm (depression)) = ',h)\n",
"raw_input('press enter key to exit')"
]
}
],
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|
