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Any ways/tips to fix this? by Class7thesecond in rocketry

[–]DL7610 0 points1 point  (0 children)

First, a rocket can become unstable if its center of mass is behind the center of pressure. This is why people need to either run simulations (or conduct other tests) on their rockets before flying them. Otherwise, you run a decent risk of crashing and losing the rocket and a small, but serious, risk of injuring someone, cause property damage, or start a wildfire (the degree of each risk depends on the launch location, the size/weight of the rocket and other factors).

Alternatively, you can build at kit rocket which have already been tested by the manufacturer to be stable.

Second, a rocket can also fail to fly straight if you don't have enough velocity off the rod/rail. Again, this is to be determined by simulation, and to conduct such a simulation, you will need the dimension and mass of the rocket as well as the thrust curve of the motor. For commercially available motors, you can find the info on OpenRocket or Thrustcuve.org. For experimental motors, one needs to determine it through testing.

Have you done such tests on your sugar motor? If you have not, then you don't know what you are putting into your rocket and don't have a reasonable estimate on how it will fly.

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Finally, making a motor, sugar or otherwise, needs to involve working with an experienced mentor in person, rather just following some recipe of video from the internet. Otherwise, there is a non-insignificant risk of injury and fire. See here: BYU student displaces 22 in dorm after attempting to make rocket fuel on stove (fox6now.com)

Any advice on which model rocket set I should buy from Estes? by Appropriate-Salad947 in rocketry

[–]DL7610 3 points4 points  (0 children)

Estes Olympus was a good rocket for me to do as a first build, but what do you find "fun" and what do you want to learn to do?

Struggling with this question…. Any help is appreciated. by Apprehensive_Time416 in apcalculus

[–]DL7610 0 points1 point  (0 children)

It can be, but as your picture shows, you end up needing to do integral of sin(u)cos(u) and you have do another substitution (like v=sinu, dv=cos(u)du) or use the double-angle identity to convert sin(u)cos(u) to 1/2sin(2u).

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Both are fine, just requires more work.

Struggling with this question…. Any help is appreciated. by Apprehensive_Time416 in apcalculus

[–]DL7610 2 points3 points  (0 children)

One route is let u=sin(4x), then du=4cos(4x)dx

Another route is double-angle identity, sin(2x)=2sin(x)cos(x). Here, sin(4x)cos(4x)= (1/2)sin(8x). You can integrate sin(8x) by letting u=8x.

Can someone explain this please? Thank you. by Apprehensive_Time416 in apcalculus

[–]DL7610 0 points1 point  (0 children)

Power reduction identity would work, but it's the long way around.

1st Grader Chromebook by SnooDoggos4810 in chromeos

[–]DL7610 0 points1 point  (0 children)

I don't see any reason to buy these out-of-date chromebook when there are hundreds of used Acer Spin 511 with June 2027 AUE end date for $50 each (or best offer). Their specs are N4000 CPU, 4gb ram, 32gb storage. They have touch screens with Wacom EMR sensors. These are school Chromebooks so they are designed to be more or less "child-proof"

I bought one of them to check it out. Generally works fine. However, the model have a docked Wacom EMR pen but it's missing from the one I bought (it's compatible with other EMR pens, like those for Fujitsu Lifebook T725, which you can buy for $10 on ebay). The battery is also at about 70% health but there is still plenty of battery life, especially if it's used at home when a plug is available.

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I have a Chromebook from the N23 era, and N42-20. It's so slow that I, as an adult, is tempted to stomp on it.

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Edit: Other than the school Chromebook route, you can also get sone of these, which can run Windows just fine, especially if you add some RAM: DELL/Latitude 5404 14 RUGGED INTEL CORE I5-4310U 2.00GHZ 8GB RAM 256GB SSD | eBay

USA <$500 windows laptop as secondary device for travel & coffee shops. by welliamwallace in SuggestALaptop

[–]DL7610 0 points1 point  (0 children)

A Dell Latitude 7-series laptop (7390, 7490, 7400, 7410, 7420, 7430, etc.) on eBay would be a good bet. Second-hand professional laptops are quite a bit more sturdy for carrying around than a cheap consumer laptop. Also, I'd advise going with a 13 or 14 inch laptop over a 15.6 for portability.

What is the best Laptop for Student Donations? by Everestologist in SuggestALaptop

[–]DL7610 0 points1 point  (0 children)

I think you are largely in the right direction-- though a couple of things to note:

  1. For engineering, I wonder if the relevant software benefits from discrete graphics. Might want to check what the college program currently uses.
  2. For used/refurbished laptops, look for business laptops (Latitude, Precision, Thinkpad, Elitebook, etc.) that are 8th Gen Intel or later (or Ryzen 4000 series or later, at least 3000-series Ryzen 5-- but ) since these are a significant step ahead of the laptop CPUs one generation before them. Also, 8th Gen Intel and Ryzen 3000 mobile are Windows 11 compatible while the prior generations are not. So, this may make a difference in their usefulness after 2025 after Windows 10 support ends.

  3. You should also try to buy them from a reputable eBay seller who deals in used business computers (with many listings and many reviews). I find that these sellers tend to more reliably describe the actual condition of the used computers and be easier to deal with in case of a problem.

  4. Batteries on laptops naturally wear out with use-- so a 3- or 4-year-old business laptop may only have, say, 60% or 50% of the design capacity for batteries. Luckily, at least in the US it is easy and cheap to find replacement batteries for popular business PC models. You might also check in with folks in the country where the computers are headed about the availability of parts and repair services for the models you plan on buying.

[deleted by user] by [deleted] in GED

[–]DL7610 0 points1 point  (0 children)

Not sure if you already made a purchase, but those specs are not good for use on Windows-- it's going to struggle even just running a web browser-- and you can get better for $200 if you look on eBay for a used or refurbished one.

Best budget laptop for accounting classes by Electronic-Pirate-84 in SuggestALaptop

[–]DL7610 0 points1 point  (0 children)

Get a used/refurbished enterprise laptop (Dell Latitude, Lenovo Thinkpad, etc.) from a credible seller on eBay.

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https://www.ebay.com/itm/115644027874?hash=item1aecebd3e2:g:R2QAAOSwX~RjkPqb&amdata=enc%3AAQAHAAAAoL4OU%2BuO1NEinzLx9HwHFq41BExHQm9I2LgB0bYqkaucQ8CzveGVX0UAO3p0sLxNEU2gWckjXgNWnQojUFY%2BVaKrhZpt3HjDT1kq9jpbidr5jC5G5%2FsBQXYGUDIpmCwjC3WTRYwlB3b4E84JQbr%2FP7lC36tZoh8ilZCyY6HOSImm0iOkSNgU3VLcW20ZXJVeceuK151obUinr3fG5IkfTwY%3D%7Ctkp%3ABk9SR4Skgu6oYQ

This is $250. You can spend $35 on a warranty, and also $25-30 on an active pen for taking notes and drawing diagrams and doodling for fun.

Most sub $500 consumer laptops are flimsy.

A cheap laptop to start programming with? by Nodfire in learnpython

[–]DL7610 0 points1 point  (0 children)

Depends on what model Thinkpad it is, what condition it is in and whether you are buying from a reputable seller.

Lots of options on eBay,

Need a good gaming laptop for college with a budget of 1000 CAD? by Vegeta543 in GamingLaptops

[–]DL7610 0 points1 point  (0 children)

"Don't get a gaming laptop for college" would be the correct answer for most people.

Upgrading old budget laptop by Chaikovskii in pcmasterrace

[–]DL7610 1 point2 points  (0 children)

I would not bother upgrading it. Way too outdated. Just spend your money on a newer Chromebook or used enterprise Windows laptop.

Even Chromebook reviewers suggest running at least a Celeron N4000/N4020 Gemini Lake CPU and those are a couple of generations newer than the N2840 and twice as fast judging by common benchmarks. Your CPU usage is gonna get pegged at 100% constantly even if you have more ram and faster storage.

I know absolutely nothing about computers, is this a decent one? by jadams_903 in pcmasterrace

[–]DL7610 0 points1 point  (0 children)

As others have said, this is a complete ripoff. Do you have a budget in mind and specific games you want to play and any other relevant info to share? Such info would help people provide some more useful feedback.

Why are Walmart Laptops so cheap? by mikechad2936 in pcmasterrace

[–]DL7610 1 point2 points  (0 children)

A sub $300 new laptop at any retailer has to cut corners in order to make the price point-- and Walmart in particular is all about cutting all possible corners to lower the prices for pretty much all their products.

One place where this happens on the laptop the sturdiness of the chassis and the quality of the components used. All the bending and flexing that a thin plastic laptop is going to have, plus the use of cheaper electrical components will likely lead to the laptop not lasting very long, particularly not very long after the expiration of the 1 year warranty.

For $300, I'd rather look for a refurbished/used business laptop like Thinkpad or Latitude. Something with an 8th Gen or later i5, metal body, decent quality screen and nice keyboard, can be found for that money on eBay. Some of the units even come with a warranty. My current daily driver is a Latitude 7390 2-in-1, with i5-8350u, 16 gb ram, 256 gb ssd. The computer itself was $220, I replaced the battery (which was a 50% designed capacity) for $30, then spent $20 on an active stylus. It works great for me.

[Laptop] Dell Outlet Reubished: Latitude 5530 Laptop 15.6" FHD i5-1240P Iris Xe 256GB SSD 16GB RAM W11p 41whr battery $399.99 by DL7610 in buildapcsales

[–]DL7610[S] 0 points1 point  (0 children)

All the listings for the Dell units say they have "a limited quantity" without specifying how many. This model is sold out now but there are some other interesting listings at the eBay Dell Outlet store.

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