X-Google-Language: ENGLISH,ASCII X-Google-Thread: f442a,aa366a233ab00d91 X-Google-Attributes: gidf442a,public X-Google-Thread: 10b271,aa366a233ab00d91 X-Google-Attributes: gid10b271,public X-Google-Thread: f996b,53f9f7cceb4d817f X-Google-Attributes: gidf996b,public X-Google-Thread: 107d75,4a81179a975b6945 X-Google-Attributes: gid107d75,public X-Google-ArrivalTime: 2002-03-28 14:07:26 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed1.cidera.com!Cidera!cyclone.columbus.rr.com!cyclone3.kc.rr.com!news3.kc.rr.com!twister.socal.rr.com.POSTED!not-for-mail Message-ID: <3CA39449.7060105@alum.rpi.edunospamm> From: Chris Wiegand User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; rv:0.9.4) Gecko/20011128 Netscape6/6.2.1 X-Accept-Language: en-us MIME-Version: 1.0 Newsgroups: alt.ascii-art,alt.flame.jesus.christ,sci.physics,alt.sci.physics Subject: Re: A question for those interested in physics... References: <56c45acf.0203281214.7c24b70a@posting.google.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Lines: 131 Date: Thu, 28 Mar 2002 22:07:06 GMT NNTP-Posting-Host: 66.91.81.204 X-Complaints-To: abuse@rr.com X-Trace: twister.socal.rr.com 1017353226 66.91.81.204 (Thu, 28 Mar 2002 14:07:06 PST) NNTP-Posting-Date: Thu, 28 Mar 2002 14:07:06 PST Organization: RoadRunner - West Xref: archiver1.google.com alt.ascii-art:16363 alt.flame.jesus.christ:74463 sci.physics:165013 alt.sci.physics:18381 Jonas M�ller wrote: > Edwin wrote in message news:... > >>"Robert Bowmaker" wrote in >>news:x7Vn8.1094$sO2.220418@news.xtra.co.nz: >> >> > >>>The question is: What actually happens to the bullet? Does it go into >>>space? Does it fall back down? Does it burn up? None of the above? >>> > > I got a bit interested in this problem so I tried to solve it, at > first mathematically but thats a bit difficult. > I came up to this differential equation > > V(t) = V(0) -g*t -cw*A*rho*t/2/M*(V(t))^2 > This is the correct equation for one way only, but you handled it appropriately in your program with a while statement. > which is to difficult to solve, so I wrote a programm to solve this > problem. > Here is it: > > ------ > import java.io.*; > public class Physik { > > // this Programm assumes constant gravity. START_VELOCITY should not > // be to close to escape velocity > public static final double START_VELOCITY=600.; //meters per > second > public static final double BULLET_MASS=.0059367; // kg > public static final double BULLET_RADIUS=0.005; //m > public static final double SPHERE_CW_VALUE=0.43; > public static final double EARTH_ACCELERATION=9.81; // m/s^2 > public static final double AIR_DENSITY=1.29; //kg*m^-3 > > public static void main(String[] args) { > double velocity = START_VELOCITY; > double altitude=0.1; > long time=0; // milliseconds > > while(altitude>0) { > time++; > if(time%1000==0) { // Output every second > System.out.println("Time: "+(int)(time/1000)+ > " sec. Velocity: "+velocity+" Altitude:"+altitude+"m"); > } > if(velocity>0) { > velocity -= (0.001*EARTH_ACCELERATION); // effects of gravity > velocity -= 0.0005*SPHERE_CW_VALUE*Math.PI*BULLET_RADIUS* > BULLET_RADIUS*AIR_DENSITY*velocity* > velocity/BULLET_MASS;// effects of air resistance > } > else { > velocity -= (0.001*EARTH_ACCELERATION); // effects of gravity > velocity += 0.0005*SPHERE_CW_VALUE*Math.PI*BULLET_RADIUS* > BULLET_RADIUS*AIR_DENSITY*velocity* > velocity/BULLET_MASS;// effects of air resistance > } > altitude += 0.001*velocity; > } > System.out.println("End"); > System.out.println("Time: "+time+" msec. Velocity: " > +velocity+" Altitude:"+altitude+"m"); > } > } > ------- > And here is the output: > Time: 1 sec. Velocity: 182.767329315557 Altitude:313.9889103484415m > Time: 2 sec. Velocity: 102.93655324264626 > Altitude:450.19204386384945m > Time: 3 sec. Velocity: 67.28102752697508 Altitude:533.4695325824632m > Time: 4 sec. Velocity: 45.885623795788625 Altitude:589.3113694914061m > Time: 5 sec. Velocity: 30.721468003701805 Altitude:627.2551712330571m > Time: 6 sec. Velocity: 18.66332461450972 Altitude:651.7606345423462m > Time: 7 sec. Velocity: 8.168188312246363 Altitude:665.085517850534m > Time: 8 sec. Velocity:-1.708012596526278 Altitude:668.2907108883071m > Time: 9 sec. Velocity:-11.331565958315913 Altitude:661.7275295391529m > Time: 10 sec. Velocity:-20.19517275872547 Altitude:645.8738977444464m > Time: 11 sec. Velocity:-27.848887324834912 Altitude:621.7352040884126m > Time: 12 sec. Velocity:-34.09827745002394 Altitude:590.6398258126908m > Time: 13 sec. Velocity:-38.972018448610804 Altitude:553.9931841438874m > Time: 14 sec. Velocity:-42.63856531226591 Altitude:513.0945060604246m > Time: 15 sec. Velocity:-45.32292568279939 Altitude:469.040225796333m > Time: 16 sec. Velocity:-47.24932123874531 Altitude:422.69864533895m > Time: 17 sec. Velocity:-48.61203334409702 Altitude:374.7273849964622m > Time: 18 sec. Velocity:-49.56622374124049 Altitude:325.60917279345995m > Time: 19 sec. Velocity:-50.2296014059005 Altitude:275.6907170908416m > Time: 20 sec. Velocity:-50.68850928763151 Altitude:225.2172953804121m > Time: 21 sec. Velocity:-51.00487835669808 Altitude:174.36062359164038m > Time: 22 sec. Velocity:-51.22246413502058 Altitude:123.2400549298544m > Time: 23 sec. Velocity:-51.371866322071526 Altitude:71.93813718527623m > Time: 24 sec. Velocity:-51.47433608682388 Altitude:20.511768627818906m > End > Time: 24398 msec. Velocity: -51.50557167546148 > Altitude:-0.032895169707768394m > > As you should see its not really important how fast the bullet is > shot, because air resistance evens the earth acceleration out. If the > bullet falls a distance of about 490 meters(after it has reached the > highest point) it gets a speed of about 50 m/s (180 km/h) which is > probably enough to be very dangerous. > > This program simulates a direct vertical shot of a spherical lead > bullet started with a 600 m/s (2160km/h). The bullet has a diameter of > 5mm and weigths 5.9376g (I do not know if this is realistic). A bullet > with a different size would probably reach an other velocity. If > there's no wind, this bullet will reach its starting place 24 seconds > after it was shot.(if there is wind, it will reach an other place in > the same time with the same horizontal speed) > > > I hop I brought some clarity into this discussion. > > > If you want to test this program you need an installed Java SDK > > Paste the programm into an editor > save as 'Physik.java' > compile: 'javac Physik.java' > run: 'java Physik' >