Air resistance

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0 height="100%"><tr> <td valign="top" width=200 BGCOLOR="#003333" TEXT="#F7F7FF" background="03fd4c00dduajq.gif"> <div> <TABLE BORDER="0" CELLPADDING="2" CELLSPACING="0" WIDTH="95" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP HEIGHT= 46 WIDTH="91"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="46" ALIGN="bottom" WIDTH="91" HSPACE="0" VSPACE="0"></tD> </tR> </TABLE></div> <div> <A HREF="index.htm" TARGET="_top" TITLE="Science For All"><U>home</U></A></div> <div> <A HREF="site_map_and_site_search_engine.htm" TARGET="_top" TITLE="Science for all site map"><U>Site map + site search engine</U></A></div> <br> <div> <A HREF="id56.htm" TARGET="_top" TITLE="Student pages switchboard"><U>Switchboard</U></A></div> <div> <A HREF="slg.htm" TARGET="_top" TITLE="solids, liquids and gases"><U>solids, liquids and gases</U></A></div> <div> <A HREF="slg_structure.htm" TARGET="_top" TITLE="Solids, liquids and gases their molecul"><U>Solids, liquids and gases - their 'molecular' structure</U></A></div> <div> <A HREF="id63.htm" TARGET="_top" TITLE="Changes of state"><U>Changes of state</U></A></div> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c8ffffff00.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Air resistance</B></div> <div> <A HREF="id79.htm" TARGET="_top" TITLE="Mass and weight"><U>Mass and weight</U></A></div> <div> <A HREF="id81.htm" TARGET="_top" TITLE="Conduction of heat"><U>Conduction of heat</U></A></div> <br> </td> <td valign="top" BGCOLOR="#FFFFFF" TEXT="#080000" bgproperties="fixed" background="0f8a0a03.gif"> <div> Air resistance</div> <br> <div> You are visiting the Science For All site</div> <div> <B><IMG SRC="0f7f4040.gif" border=0 width="500" height="4" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <br> <div> <B>What is air resistance? </B></div> <div> Basically, it is <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >friction </FONT>between an object and the <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >air</FONT>.</div> <br> <div> <B>What causes air resistance?</B></div> <div> All matter is made from <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >atoms </FONT>and/or <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >molecules</FONT>. The air is no exception. When something moves through the air, it <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >bumps </FONT>into the atoms and molecules. Take for example a car:</div> <br> <DIV ALIGN="LEFT"></DIV> <div> <IMG SRC="184ea6f0.gif" border=0 width="234" height="111" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div> <IMG SRC="17fe4ef0.gif" border=0 width="484" height="239" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <br> <div> Even though atoms and molecules are very <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >tiny </FONT>and very <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >light</FONT>, each <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >collision </FONT>causes a <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >force </FONT>on the moving object (the car) The force from <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >each individual collision</FONT> is therefore very tiny. There are however <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >millions </FONT>of these collisions each second so millions of tiny forces <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >add up </FONT>to make a <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >large</FONT> overall force. </div> <br> <div> <IMG SRC="187e6640.gif" border=0 width="486" height="356" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <br> <div> It is this big force that is called air resistance.</div> <br> <div> What happens to the size of the air resistance force as the speed increases?</div> <br> <div> If the car is going <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >faster</FONT>, then it will hit the atoms and molecules of the air <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >harder</FONT>. This means that the tiny <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >forces </FONT>will be <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >bigger</FONT>. This in turn means that the <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >air resistance</FONT> force gets <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >bigger</FONT> as something moves <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >faster</FONT>. </div> <br> <div> You can feel this happening when you walk and run. When you walk, unless it is windy, you do not normally notice the air resistance because it is very low (collisions are not very hard). When you run, you can readily feel the air resistance on your face.</div> </td> </tr></table></body>