How do you find the center of pressure and the center of gravity on a bottle rocket? and what is it?
597906
In school, I used a CAD program to draw and design a rocket made from a soda bottle. In making this, we had to be aware of two important concepts: center of pressure and center of gravity. The center of pressure is the point at which all pressures are centered. This is basically the line at which there is an equal surface area of rocket above and below it.\nThe center of gravity is the line at which there is an equal amount of mass above and below it. For a rocket to fly properly, the center of mass needs to be situated the average diameter of the rocket above the center of pressure.
190039
Just watch a NASA space rocket take off. \n\nThe enegergy created to get a rocket off the ground and into space comes from the power generated by the controlled mixing (fusion reaction) of liquid Hydrogen and Oxygen.
731455
Something that may be fun is a project with model rockets. Give them the necessary information to calculate the height of the rocket, based on the rocket engine and mass of the rocket as homework.\n\nThen at school, fire a few of them and using basic trig calculate the height and see how close they are.\n\nRocket engines are typically rate something like: A8-3 which breaks down as follows:\nA --> 2.50 Newton-seconds of power\n8 --> average thrust (in newtons)\n3 --> seconds from end of thrust to ejection charge (parachute)\n\nThe engines also have a time-thrust curve that shows how the power is delivered over time. Check the following link below for some more info:\n\n------------------------------------------------------------------------\n\nHere is another one:\nNot sure how readily available props are for you but if you can hook up a camera in a room with a strobe light/flash and then set up a collision (air hockey table or pool table come to mind) then you can calculate the velocity of each object, measure its mass and then demonstrate the conservation of momentum using vectors. Because you know the frequency of the strobe, and the distance traveled, you can compute the vector velocity.\n\nOr how about:\nFirst, fire an arrow down a football field. Given the amount of time aloft calculate the initial velocity (ignore air resistance/friction) Then fire an arrow at a bale of hay (extend the bow by the same amount) and measure how far into the bale the arrow went. Using the same initial velocity and distance into bale, calculate the rate of deceleration and coefficient of friction of the hay bale.
834801
the geometrical center and center of gravity match only for object that have symmetrical shape (around an axe or point: like a cylinder or sphere) and a constant density
841719
sorry for laughing but I know everything can be used with math. Those rockets, how long is goes up, where it lands the wind , angle bla/bla
835572
Gotta approach this using basic principles.\n\nEnergy is the integral of force applied over a distance.\nTheres two sets of forces working:\nfluid and gravitational.\n\nSo you make your control volume, and look at it.\nYou want to raise the water in it, thats mgh or rho*v*g*h\n\nYou also have to exert a pressure to push against the water ahead of it.  The downward pressure acting on your control volume is f/a so the force you must overcome is p*a and you are traversing distance h so the energy is p*a*h\n\nTherefore to raise the fluid vertically against a down pressure and against gravity the minimum energy (real world is lossy) is \nE = h*(mg+pa)
1010543
Suppose you are taking a space walk near the space shuttle, and your safety line breaks. How would you get back to the shuttle? The thing to do would be to take one of the tools from your tool belt and throw it is hard as you can directly away from the shuttle. Then, with the help of Newton's second and third laws, you will accelerate back towards the shuttle. As you throw the tool, you push against it, causing it to accelerate. At the same time, by Newton's third law, the tool is pushing back against you in the opposite direction, which causes you to accelerate back towards the shuttle, as desired. This is the principle behind jet propulsion: a jet rocket expels fuel rapidly by ``pushing against it''. By the third law the fuel exerts an equal and opposite force against the rocket so the rocket accelerates in the opposite direction that the expelled fuel goes. Another example of the 3rd law is a book lying on a table. If the table were not there the book would fall under the force of gravity between the book and the earth. Why then doesn't the book move off the table, in accordance with the 2nd law? The table is exerting a force on the book that is just enough to cancel the gravitational force on the book. By Newton's third law, the book is also exerting an equal and opposite force on the table, and this is why the table feels the weight of the book. If the book were very heavy, its weight would cause the table to bend, or even break. This is illustrated in the following figure. \n\nThe answer to this question comes from the third law. Imagine the skateboard again. On the ground, the only part air plays in the motions of the rider and the skateboard is to slow them down. Moving through the air causes friction, or as scientists call it, drag. The surrounding air impedes the action-reaction. \n\nAs a result rockets actually work better in space than they do in air. As the exhaust gas leaves the rocket engine it must push away the surrounding air; this uses up some of the energy of the rocket. In space, the exhaust gases can escape freely.
434799
Exhibition of centrifugal force.  Using an empty bottle, drill a hole through the cap and the bottom of the bottle.  With a large enough rubber band, attach it to a tiny bar and insert it into the bottle via the hole in the bottom so that the tiny bar acts to fasten the the band to the bottom.  Then from the inside of the bottle pull (stretch)the band out and make it pass though the bottle cap, and attach it to a wooden bar twice the length of your usual pen.  So, if done correctly, you'd have your rubber band stretched from the bottom of the bottle all the way to the cap where the wooded bar is.  This is done in such a way that when you turn the wooden bar the rubber band winds up, so that when you release, it unwinds, you getting the picture?  Now, attach two small plastic cups to both ends of the wooden bar, maybe by thumbtacks or something, fill it up with seeds or liquid.  Now, when you turn the bar a few times and release it, you see the bar unwinding and the cups filled with water starts to rise as an effect of centrifugal force.
472077
When I was a kid, my brother tied pop bottle rockets to a milk crate in an attempt to get to the moon. I was worried that he wouldn't make it in the three seconds before they popped, so I took them all off. You can try it though, it just might work.
83009
Center of gravity is not a point but is a line of action of force...\nSince a line is of infinite lenght there is no way you can think of the center of gravity of an object which does not pass through the object.\n\nhttp://www.schoolingkids.com/\n\nhttp://www.futureaccountant.com/
871968
Here is the math for finding our solar system's barycenter. (It's under the heading "Barycenter").\nhttp://en.wikipedia.org/wiki/Center_of_mass
317575
This is actually pretty easy.\n1) Take a 2 liter bottle and poke a hole in the cap (with a sharp knife or philips head screwdriver) just a bit smaller than the diameter of a straw.\n\n2) Get a straw and force it through the hole in the lid. The straw should be made out of a fairly strong substance.... perhaps like a curly straw. The curly straws actually have straight sections. If the straight section is at least 3 inches long, it should work to go ahead and cut it. If the straw jams too tightly in the lid, it will obstruct the flow so just cut the hole slightly bigger until you get the right fit. We just want the straw to fit REALLY snug.\n\n3) position the straw so only a small length of it is pointing out the bottom of the cap (the longer portion should be sticking out of the top of the cap acting as a nozzle). Once the straw is placed, you could use a little epoxy or tape just to keep it from coming out.\n\n4) Get a small water balloon. Lower it into the opening of the bottle but DON'T LET IT FALL IN!!!!  While holding the opening of the water balloon above the opening of the bottle (with the rest of the balloon hanging inside the bottle), fill the balloon with vinegar so that it takes up about half the volume of the bottle. Once this is done, tie off the top of the water balloon and let it drop into the bottle. You may want to hold the bottle on it's side so the balloon doesn't smack the bottom of the bottle. Then slowly tip the bottle back up.\n\n5) Now, carefully fill the remaining space in the bottle with baking soda. (we don't want the balloon to pop YET)\n\n6) Put the lid back on the bottle and stick a piece of chewed gum just barely in the outside opening of the straw. This will preserve the baking soda by not letting any excess moisture in while the fire extinguisher is not in use. Make sure that the gum is not in too tightly or too far as we want to be able to remove it quickly.\n\n7) You are done!!!!! To use it just remove the gum and smack the bottle on a hard surface so the balloon breaks inside the bottle. When the balloon breaks, the vinegar and baking soda will mix, react, cause pressure, and the pressure will be released through the straw and in the direction that you point the fire extinguisher  : )\n\nHope this helps\nThanks\nJon
720092
While the answers above are correct, I will go a bit further.\n\nEstes rockets sells a nice tool for just this very job that will make your measurement fairly easy and accurate. It is called AltiTrak (TM).\n\nhttp://www.estesrockets.com/cgi-bin/products.cgi?view,296
157080
This is just the regular projectile motion problem (see your text) just with an added initial velocity in the x direction (the velocity of the ship).\n\nLet's take as our positive direction the direction the gun shoots. (That is, the ship is moving in the negative direction.) Thus, the initial x component of velocity of the projectile is the x-component of the guns velocity less the velocity of the ship. (I'm going to use Vo for the initial velocity, since using "not" as a subscript confuses me.)  And I'll use A for alpha to save space.\n\nVxo = Vo cos(A)- v\nVyo = Vo sin(A)\n\nOur equations of motion are\n\nX = Xo + Vox t + 1/2 ax t^2\nY = Yo + Voy t + 1/2 ay t^2\n\nTo find the range, we want when the projectile splashes back down again, i.e. Y = 0.  If we set Xo = 0, then X will be the range, i.e. the X position when Y = 0 again.  And there is no acceleration in the x direction, the y acceleration is -g, the acceleration of gravity.  Plugging all that in, we get\n\nR = Vxo t \nR = (Vo cos(A) - V) t                     (1)\n\n0 = Vyo t - g t^2/2\nVyo t = g t^2/2\nVyo = g t/2\n2 Vyo/g = t\n2 ( Vo sin(A)) / g = t                     (2)\n\nPlugging our expression for t (Eqn. 2) into Eqn. 1 yields\n\nR = (Vo cos(A) - V)2 ( Vo sin(A)) / g \n\nwhich is the formula you gave.\n\nTo find the max range, we can use calculus.  There may be a more straightforward way if you don't know calculus, but this works for me.\n\nThe range formula is a function R of variable A.  To find the max, take the derivative and set it equal to 0.  Thus\n\ndR/dA = 2 Vo/g [sin(A)(-Vo sin(A)) + (Vo cos(A) - V)cos(A)]\n       =2 Vo/g [-Vo sin^2(A) + Vo cos^2(A) - V cos(A)]\n\nusing a trig identity\n\n       =2 Vo/g[Vo cos^2(A) - Vo + Vo cos^2(A) - V cos(A)]\n       =2 Vo/g[2Vo cos^2(A) - V cos(A) - Vo]\n\nWhat we have here is a quadratic equation with the variable cos(A).  When we set it equal to 0, in order to find the minimum, we can use the quadratic formula.\n\ncos(A) = (- (-V) + SQRT[V^2 - 4(2Vo)(-Vo)])/2 (2Vo)\n        = (V + SQRT[V^2 + 8Vo^2])/4Vo
1185755
This is how to do it, I have done it 1 month ago in school.\n\nMaterials Needed:\n1)Plastic Soda/Water/Juice Bottle.\n2)Liquid, you have to fing the correct combination of liquids to use, and see which liftoff was the best and try to be creative, don't blow yourself or your house up, though.(we did at school)\n3) I believe it is a pumper, you could search it online as "water bottler rocket launcher" on Yahoo. I THINK it's around $60:)\n4) materials you want to decorate your rocket with(leave the inside empty)\n\n\nInstructions:\n1)Decorate your bottle, don't make it too heavy though.\n2)Find the best liquids that mix to make the rocket's liftoff better, or buy it from someone(remember to buy it legally).\n3)Mix the liquids, be safe and don't blow up anything.\n4)Insert the liquid in the hollow bottle, and immediately insert the top(the side you drink with) in the whole, make sure the launcher you buy fits the size of your bottle.\n5)Push the red(or any other color button), the rocket might start to shake, that it OKAY.\n6)Let an ADULT, hold the string, and count down.\n7)The string is jerked, and the rocket is lifted off.\n\nRemember, these instructions might vary from launcher to launcher, and to be safe when mixing liqiuds, mix safe liquids like orange juice and apple juice!\n\nAnd be safe..............
844533
from what I remember conservation of momentum states that: \nm1v1=m2v2\nwhere in this case, m1= mass of the astronaut\nm2=mass of the sat.\nv1= unknown\nv2=speed of the sat.\n\nyou can find the speed by solving the above equation for v1:\nv1=m2v2/m1\n\nFrom there, once you have the speed you can calculate the distance by multiplying the speed (v1) times the time (7.5 s) given in the problem.
902905
Ok. this is simple. u need to know about buyoancy, like how air is lighter than water. all you really got do is put some small weights (ex. paper clips, rocks, etc) in the bottle. have it so that it will just barely float. then cut a hole to the side and insert the end of a tube in it. make sure it is water tight. then place it in a tub. it shold float, when you suck on the end of the tube, it should take some of the air out making it less buoyant, and therefore it will sink. there are also many other ways to do this that will make it function more like a real submarine like putting the bottle with weights inside and somehow add pressure to the the outside of the tube to compact the air inside the bottle, causing it to sink. good luck on your project