Transfer and Conversion of pressure to Energy (Kinetic)

[BatmanACC]

Simple problem here boys. I'm currently in the process of making a high powered and hand held potato gun. Essentially, it'll function just as a regular paintball gun would but on a slightly larger scale. Now...What makes this a rather hard endeavor is that I want to shoot a whole potato; and that is some serious weight. So before I start construction I want to get the physics behind the gun down pat.

It'll be a bolt like design whereby a pressure source pushes the bolt forward into a spring that later retracts the bolt into its original position but not before the bolt hits and ejects the potato out the barrel.

Here's what I got. Okay so the Kinetic Energy of the Bolt when it hits the patato is

1/2mv^2 - Fpvc = K1

Where Fpvc = force of friction done on the bolt by the PVC pipe (probable material)

And again, we equate K1 to

1/2mv^2 - Fpvc = K1 = K2

Which is the equation for the potato when it exits the pipe. This, so we can calculate the velocity at the time of exist.

That's not to complicated; unless I'm forgetting something in that calculation? I don't think so because

M1V1 + M2V2 = M1V

Where M1 = mass of patato and M2 = mass of bolt. Therefore M1V2 = 0 and M2V2` = 0.

Hence

M2V2 = M1V

And the only reason Kinetic Energy wouldn't be conserved is due to Friction correct?

Okay so assuming the above calculations are right (if there not do let me know) I need to know the relationship between pressure, the resistance of the spring that the bolt is propelled into, and the weight of the bolt.

Because I need to calculate the minimum pressure to meet my goals (in terms of distance and speed). Does anyone know the constraint relation for those 3 things? The mass of the bolt, the resistance of the spring and the weight of the bolt?

 

[eljose79]

I am glad to see your enthusiasm for creating a high-powered potato gun. I can offer some insights and suggestions for your project.

Firstly, your equations for calculating the kinetic energy and velocity of the bolt and potato seem correct. However, there are a few factors that you may want to consider in your calculations.

1. Friction: As you mentioned, friction will play a significant role in the velocity and energy of the potato. In addition to the friction between the bolt and the PVC pipe, you should also consider the friction between the potato and the pipe, as well as the air resistance as the potato travels through the barrel.

2. Air pressure: The pressure of the air inside the gun will also affect the velocity of the potato. The higher the pressure, the more force it will exert on the bolt, resulting in a higher velocity.

3. Spring resistance: The resistance of the spring will also impact the velocity of the bolt. The stronger the spring, the more force it will exert on the bolt, resulting in a higher velocity.

4. Mass of the potato: While you have included the mass of the potato in your equations, it is also important to consider the shape and size of the potato. A larger and more irregularly shaped potato will experience more air resistance, resulting in a lower velocity.

To calculate the minimum pressure needed to meet your goals, you will need to consider all these factors and make some assumptions about the values of friction, air pressure, and spring resistance. You can then use the equations you have mentioned to calculate the velocity and distance of the potato.

In terms of the constraint relation between the mass of the bolt, spring resistance, and weight of the bolt, it is not a simple relationship. The force exerted by the spring will depend on its stiffness and compression distance, and the mass of the bolt will also play a role in determining the velocity. It would be best to use a numerical approach or conduct experiments to determine the minimum pressure needed for your desired velocity and distance.

I hope this helps and good luck with your project! Remember to always prioritize safety when working with high-powered devices.

 

[astrokreng]

I appreciate your enthusiasm and attention to detail in this project. It seems like you have a good understanding of the basic physics principles involved in your potato gun design. However, there are a few points that I would like to clarify and expand upon.

First, let's discuss the conversion of pressure to kinetic energy. In your design, the pressure from the air source is used to push the bolt forward, which then hits the potato and transfers its kinetic energy to the potato. This is a simple example of energy conversion, where the potential energy of the compressed air is converted into kinetic energy of the potato.

However, in order to accurately calculate the velocity of the potato, you also need to take into account the energy lost due to friction. In your equation, you have accounted for the force of friction on the bolt, but you also need to consider the friction between the potato and the barrel of the gun. This may be more difficult to calculate, as it will depend on factors such as the surface roughness of the barrel and the speed of the potato.

Secondly, I would like to address your conservation of energy equation. In this case, it is important to remember that energy is conserved, but momentum is not. The momentum of the bolt and the potato may be different, but their total kinetic energy should be the same before and after the collision.

As for the relationship between pressure, spring resistance, and bolt weight, it is a bit more complicated. The pressure will determine the initial velocity of the bolt, which will in turn affect the force exerted on the spring. The resistance of the spring will also affect the velocity of the bolt, as a stiffer spring will require more force to compress and therefore result in a higher velocity. The weight of the bolt will also play a role, as a heavier bolt will require more force to accelerate to the desired velocity.

To calculate the minimum pressure needed for your desired distance and speed, you will need to consider all of these factors and possibly do some experimentation to find the optimal combination. Keep in mind that there may also be other variables at play, such as air resistance and the aerodynamics of the potato.

In summary, your understanding of the basic principles involved in your potato gun design is a good start. However, to accurately calculate the velocity and distance of the potato, you will need to take into account factors such as friction and the relationship between pressure, spring resistance, and bolt weight. Good luck with your