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Joined 2 years ago
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Cake day: July 3rd, 2023

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  • Maybe I should have included another object for scale. It was advertized as a grapefruit of variety “Sweety”. According the Wikipedia it’s also known as an “Oroblanco”, and the color is typical. In any case it tasted alright for a foreign fruit in winter for 79 cents :D I liked that the flesh was very easy to scoop out.









  • I’m not sure about the standard - but in my experience, if a PD trigger IC requests 12V, that will be supplied, no matter the current draw. I have used this to power several low power devices, for example a 12V computer fan, and I have also verified this with no load at all. There is also PD PPS, which could be used to deliver 14V or any other voltage.

    Edit: I normally use this kind of trigger board, they are available everywhere online.






  • Aerospace engineer here. To levitate, the force of the exhausted mass flow (F=ṁ×v) has to equal the pull of gravity (F=m×g) on your body. The gravity of earth is g=9.81N/kg. Wikipedia says the average body mass is 62kg. It also says the bladder capacity of an adult is about 400ml, and I’ll assume the density to be 1kg/l. You want to levitate for 2 seconds, so your mass flow needs to be ṁ=0.4kg/2s=0.2kg/s. If you rearrange the equation, you get v=m×g/ṁ=62kg×9.81N/kg/(0.2kg/s)=3041m/s.

    So if you manage to pee with a velocity of about 3km/s, you can levitate for 2 seconds with an average sized bladder.

    To achive that, your “exhaust” must be clenched to a diameter of about 0.29mm. This gives a cross-section of 0.066mm² or 6.6×10^-8m². Multiply that with the velocity of 3041m/s and you again get your flow of 0.2l/s.

    Of course, during those 2 seconds you loose mass and therefore, earth’s pull on you gets less and you start to accelerate to about 0.23km/h, reaching a height of 4cm. If you took your special bladder to space, we can use the rocket equation to calculate that this stunt would accelerate you to 3041m/s×ln(62kg/61.6kg)=19.7m/s=71km/h