When Does the Air Resistance Force Make a Difference?
Step 2 — Tape one end of one piece of string to the first ping pong ball. Tape one end of the other piece of string to the second ping pong ball. Step 3 — Hang the other end of the string to a stationary object. The objective is for the ping pong balls to hang freely in the air at the same level and about 4 inches apart. Helpful Tip: We used a clothes drying rack. You could also tape them to a door frame or hand them to a shower curtain rod.
Step 4 — Make sure the ping pong balls hang in mid-air at the same height about 4 inches apart. Now ask a few questions. What do you think will happen if you blow air between the two ping pong balls? Do you think the air will cause them to move?
In what direction? Write down your hypothesis prediction and then follow the step below. Step 5 — Use a drinking straw to blow air directly in between the ping pong balls. Position yourself so the straw is level with the ping pong balls and about 4 to 5 inches behind them. What happens to the ping pong balls when you do this?
Now, take a moment to write down your observations. Was your hypothesis correct? Do you know the reason why the ping pong balls moved toward one another? Find out the answer in the how does this experiment work section below. Air pressure is the pressure caused by the weight of a column of air pushing down on an area. Air pressure can decrease when air is in motion. When you blow air between the ping pong balls in Step 5, you cause the air between the ping pong balls to move faster, lowering the air pressure between them.
The air on the outside of the ping pong balls is relatively still compared to the moving air between the ping pong balls, resulting in high pressure on the outside of the ping pong balls.
This high-pressure air on the outside of the ping pong balls moves toward the lower pressure air between the ping pong balls and it pushes the ping pong balls together in the process.
Fluids like air or water flow from areas of high pressure to areas of low pressure. Other Ideas to Try Try using empty soda cans instead of ping pong balls.
Do the soda cans behave in the same way as the ping pong balls?
Ping Pong Parachute Air Flow
Also, non-eBay tools tend to last longer, so you won't have to buy a new soldering stand every year, for example. It's OK to buy electronics from eBay most of the time , especially if it's generic- but expect weeks delivery from most Asian sources. The Arduino Nano can be bought from ebay as well, but I recommend purchasing one from a website such as sparkfun or robotshop as the quality is guaranteed in the two latter cases. Start by removing labels and bottle caps from the bottles.
If you have difficulty in doing so, rinsing under warm water helps. If the label is really tight, or made of plastic, then you don't need to take it off. Then, measure the diameter of the bottle and record it. With an X-acto knife, cut off the top of one of the bottles around 1cm from the start of the neck.
Also, cut off the bottom of the same bottle around 25 cm from the top, so you end up with a cylinder with one tapered edge, open at both ends. The smaller end should measure around 2. Please keep the cut-off section- you'll need it. Cut away half of the ping-pong ball, and carefully glue it to the interior of the tapered end of the bottle, flush to the cut edge.
You want to end up with a nose cone that has the profile of a parabola. It may take a few attempts to secure the ping pong ball, so it does not fall off. It helps to hold the shell upside down while the glue cools. Once the glue has set, move all of what you just made to the side, but remember not to throw it out by accident Step 9: Rocket Structure, Part 2- Parachute Chamber You will now need to build a parachute and control systems chamber, which houses the Arduino, electronics modules and the servo, as well as the parachute itself.
Please note that I used cardboard, a material that has almost identical structural characteristics to corrugated plastic, because I did not have the plastic available to myself at that moment. You should be able to follow all the steps in the exact same way. In fact, you can use cardboard as well, but if it gets wet you'll have a problem.
Start by taking your piece of corrugated plastic and cutting out 2 identical circles for lack of better word with an X-acto knife 1. The circles should have the same diameter as the bottle, hopefully you followed instructions and recorded the value earlier. Cut out a rectangle with a length of 10cm and a width equal to your bottle diameter 2. Score the rectangle along its middle in such a way that the knife only cuts through part of the material 3. This will let you bend the plastic without having it snap into two pieces.
Lay the rectangle before you in such a way that it bends vertically inwards relative to you 4. On the right half of the bent plastic, cut out another smaller rectangle in the top middle area- the exact location does not matter 5. In most cases, the dimensions are somewhere around 1. Take one of the circles and lay it flat. Hot glue on the bent rectangle in such a way that both bottom corners are resting on the circumference of the circle 6.
You should ensure that the whole bent rectangle is flush with the circle. Glue on the top circle 7 making sure the same conditions are satisfied as with the bottom one. Using the thick color paper, reinforce the joints by cutting out L-shaped brackets and glueing them on.
You should end up with something that resembles the assembly in picture 8. Step Electronics Work Build the electrical circuit shown in the fritzing diagram. Start by soldering the perforated boards. I recommend soldering the components in a very compact layout, as you will need to fit them inside the bottle rocket. Refer to the three photographs of the modules for approximate layout and size planning.
Please do not attempt to follow all connections- it's much easier to follow the diagram Once the modules are complete, you can start to finish the circuit by interconnecting the modules where necessary. When doing this project, I soldered male header pins onto the Arduino and used female to male jumper wires, so I could plug in the connections.
I did this because I didn't want to unsolder all the wires once the project was done- I suggest you do the same, especially if your Arduino came with header pins. Otherwise, you can buy them separately or omit them entirely.
You'll notice that I didn't build the exact design that I've provided a fritzing diagram for, the reason being that It's not the most compact design. Ensure that everything works before you put it in the rocket- it's a pain to have to take everything apart trust me, I've done this the first 3 times in a row.
Step Finishing It Off Now you'll need to put it all together-and first, position the servo motor in the cavity you've cut out, by inserting it in from the outside. Hot glue it into place. Install all the electronics in the corrugated plastic structure you built earlier. You can hot glue the perfboards into place, or tape them.
Ensure you have space for the 9V battery, and don't forget to plug it in. You should, with a well-built circuit, have enough space for everything.
Slide on the top shell, with the nosecone, and, with a permanent marker, draw out the contours of the parachute chamber and a square about 1'x1' around the servo. Take off the shell and cut those sections out. The servo cutout should look similar to 1. Put the shell back on, and trim if necessary. Make sure the nosecone is still removable for access to the servo. Take some of your leftover material, and cut out a flap about 2 cm longer and wider than the cutout for the parachute chamber. Tape it in place 1 cm back from the chamber, so that it can fully cover the opening when closed.
Cut out another flap about the same length but a little thinner and tape it inside the parachute chamber, so it springs out naturally, but can be depressed inwards. This is the ejection plate.
See the diagram. Cut a small hole at the swinging end of the cover and thread a rubber band through it. This will go to the servo arm later on.
Cut out holes for access to all the switches for control. You can do this with an x-acto knife. Step Fins Fins can be any shape you want, at this level. You can make them out of anything you want, as long as it isn't sharp and won't shatter, and it shouldn't be excessively heavy. Generally I use corrugated plastic for the fins in a simple rectangular form, maybe a little tapered from the top. I like to align it so that air passes right through it, i.
I hot glue paper brackets to the sides, then hot glue and tape the brackets to the body of the rocket. Try to use three fins, four at most. Make sure they are evenly spread out along the circumference of the body, and mount them as far back as possible. This will make your rocket fly straighter. If you want your rocket to fly without spinning, the fins must be absolutely straight.
Even a slight tilt on one of them will spin your rocket. Step Parachute Parachutes vary widely. The standard parachute for a model rocket is an octagon with a small hole in the middle, and one hole at each corner by which cables are attached or strings. These cables lead to a common anchor on the rocket body.
In my case I just attached to strings to the rocket with a simple noose around the body, but you can be more elegant if you wish. Generally you have to fold parachutes so that they fit in the chamber.
I do this by taking the middle in one hand, bringing together all of the ends in the other hand, then rolling up the parachute. Then I wrap it in the parachute cord itself until there is about 10 cm of free cord, so that the parachute can actually be pushed out of the chamber.
Step Code The code is attached below. Code is explained in the script. If any questions arise, I'll be happy to answer them in the comments. Please keep in mind that I wrote this code a long time ago and it's not the most efficient way to get the job done- but it works. I'll be updating it when I get the chance. I plan to make another tutorial devoted to that subject. The pictures show the launchers we used; this first is the school one and the second is a gardena launcher.
I suggest you visit www. Otherwise, many retail stores sell simple rocket launchers that will do the job. The program has embedded notes that explain the launch options and procedure. There are two modes, launch triggered and timer, each of which has a programmable parachute deploy delay. Before you do anything, you need to test the deployment mechanism. Follow the guidelines in the code.
If the circuit doesn't work, follow standard troubleshooting guidelines to fix the problem. Check to make sure the servo successfully unlatches the chamber cover, and that the parachute is hurled out enough to start unwinding. It would help to do a drop test to make sure your parachute is functional.
Do not pressurize above 80psi under any circumstances. Ideally, you would conduct burst tests on the pressure chamber you are using, but I think that in this case it is unnecessary.
How To Make A Parachute
It was excellent. I really think we can do it this year. After a scoring error was fixed by tournament officials, Blue Valley North finished in third place, and Mill Valley finished in fourth place. He is undertaking the position of JagWire editor-in-chief.
Ping Pong Parachute Fundamentals
When he is not reporting the news, Tanner can be found acting as the president of Youth for Refugees and taking way too many AP classes. Modeling Air Resistance Let's say I drop a ping pong ball. As it falls, I can draw the following force diagram. This typically has a value around 1. The cross sectional area of the object A.
The drag coefficient C. This depends on the shape of the object. For a spherical object, a unitless value of 0. The magnitude of the velocity squared.
The faster you go, the greater the air resistance force. The direction of the air resistance force is in the opposite direction as the velocity of the object. That's why there is a negative sign in the expression along with the r - hat which is a unit vector in the direction of the velocity. But how do you find values for the drag coefficients for different objects? The real answer is that you must measure them experimentally.
However, Wikipedia has a nice list of some values. What about a falling human? I often have to model the motion of a falling human, but there isn't a C value listed. There is one trick I can use. The trick involves terminal velocity. Suppose a human jumps out of a stationary hot air balloon.
At first, only the gravitational force acts on the human giving an acceleration of However, as the human increases in speed, the air resistance force also increases. At some point, the air resistance force will be equal in magnitude to the gravitational force and the human will no longer increase in speed. We call this "terminal velocity". Now for the trick. It seems to be mostly accepted that the terminal velocity for a skydiver is about mph Of course, this is the terminal velocity for the normal skydiving position with head facing down and arms and legs spread out.
If I guess at a human mass of 70 kg, I can set the air resistance and gravitational forces equal. Also, for simplicity I am going to call all the constants in front of the velocity squared just K since they don't change.
I only need the mass and the terminal velocity and I can build a model for air resistance. I plan to make another tutorial devoted to that subject. The pictures show the launchers we used; this first is the school one and the second is a gardena launcher. I suggest you visit www. Otherwise, many retail stores sell simple rocket launchers that will do the job. The program has embedded notes that explain the launch options and procedure. There are two modes, launch triggered and timer, each of which has a programmable parachute deploy delay.
Before you do anything, you need to test the deployment mechanism. Follow the guidelines in the code. If the circuit doesn't work, follow standard troubleshooting guidelines to fix the problem. Check to make sure the servo successfully unlatches the chamber cover, and that the parachute is hurled out enough to start unwinding.
It would help to do a drop test to make sure your parachute is functional. Do not pressurize above 80psi under any circumstances.
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Ideally, you would conduct burst tests on the pressure chamber you are using, but I think that in this case it is unnecessary. I claim no legal responsibility if you injure yourself or cause property damage, and that will not happen if you follow what I have just told you. Finally, I do not recommend trying to achieve anything other than maximum altitude, as this is by far the safest and the rocket is more likely to come back intact.
Generally you want to keep the launcher pointing straight up, but in very strong winds it's a good idea to tilt it into the wind a little bit. If you want, a launch angle of 45 degrees to the ground will give you maximum distance lengthwise, but there are few practical applications that would use that sort of thing.
As well, the parachute is likely to get ripped off during flight otherwise it would be deployed at a near-motionless moment, at apogee, if launched vertically.
Launching a rocket, especially with fins and low coefficient of drag, is extremely dangerous. Only do this if you have cleared the range and are sure that it won't hit anyone. Step Launch Videos The above one is the project build launch.
Scroll to to see the launch. It may appear to not have deployed anything as the descent speed was rather fast but the wind was strong so I was using a small parachute. Below is video from an earlier prototype. Step Improvements I've already mentioned that my goal here was to get you started with rockets.
I recommend a GoPro for it's small size and durability. Add a barometric altimeter- On eBay you can find barometric altimeters for very cheap. These use air pressure in fact they are just air pressure sensors to return values that can be used to calculate air pressure air pressure decreases with altitude.
You can use this to deploy your parachute at a better moment when altitude starts to drop. Add a data logger- Adding a data logger easiest would be the use of an SD card module to interface with Arduino will allow you to store a lot of data, such as temperature, altitude, etc. Later you can call the variables in the code and display them in a graph of some sort. Increase rocket capacity- You can splice two bottles together, and chain these splices with one another to increase the volume of your rocket and consequentially it's maximum altitude.
Increase maximum pressure- You can cover your pressure chambers with fiberglass, which will help cope with additional pressure. This can also be done by putting a second layer of the same bottle over top, then wrapping everything in electrical tape as in the very first photo.
I don't recommend this because this means you will need a remote launching system, as higher pressures mean more dangerous explosions, if your rocket does burst. This can be quite dangerous and will be done at your own risk. Additionally, this should only be attempted after you have fully acquainted yourself with the subject and conducted extensive burst tests in a safe environment. Different recovery device- We used the most popular recovery device there is- the parachute.
Air Pressure Impact on Ping Pong Balls Science Experiment
What about a glider? Or a retrograde rocket right before impact, like the Spacex Falcon 9? According to my research, no one has yet to build a water rocket with a working retrograde recovery system Add boosters- This does require additional outlets on the launchpad, but will increase your final velocity.
Add a second stage- Again, you are increasing your final velocity by giving the first stage a boost. Reach space ,ft - Although this cannot be done with 2L pop bottles, why not think about it? I am envisioning a lightweight aluminium chamber that could withstand in excess ofpsi, at a dry weight of 30 kg. This, according to my calculations, would reach an altitude of ,ft, or roughly one-third of the way to space.
Sure, it might be expensive, but it would be interesting to try, if you had the time and money. It might even become mainstream later on. Conduct experiments in microgravity- If you've ever wondered what happens to something at 0-G, then you can use your rocket to test a theory out, as there is a moment of weightlessness at apogee. Even further Please leave a comment if you have ideas and I'll add it here if it's suitable.
The more the better!