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How to Easily Locate the Accelerometer in an iPhone

Everyone should probably know that I’m obsessed with both physics and smart phones. If I can use my phone for a physics experiment, I’m good to go. That’s exactly what I am going to do right now—use some physics to find the location of the accelerometer in the iPhone 7.

Your smart phone has a bunch of sensors in it. One of the most common is the accelerometer. It’s basically a super tiny mass connected with springs (not actual springs). When the phone accelerates in a particular direction, some of these springs will get compressed in order to make the tiny test mass also accelerate. The accelerometer measures this spring compression and uses that to determine the acceleration of the phone. With that, it will know if it is facing up or down. It also can estimate how far you move and use this along with the camera to find out where real world objects are, using ARKit.

So, we know there is a sensor in the phone—but where is it located? I’m not going to take apart my phone; everyone knows I’ll never get it back together after that. Instead, I will find out the location by moving the phone in a circular path. Yes, moving in a circle is a type of acceleration.

Of course you already knew that circular motion was a type of acceleration. Yes, you knew this because you have been in car (you have probably been in a car). It turns out that the human body can also feel accelerations—although we sometimes confuse these accelerations with gravitational forces, but we can still feel them. If you are sitting in a car seat and the vehicle speeds up, it accelerates and you can feel that. Now if that car is turning in a circle, you can also feel it. That turning car is accelerating—even if it travels at a constant speed.

If you want to really understand why circular motion is a type of acceleration, you need to start with the definition of acceleration.

Here the Δ means “change in”. So the acceleration is the change in velocity divided by the change in time—that is a rate. But here is the key point. Both the acceleration and velocity are vector quantities. This means that they depend on direction as well as magnitude. Since the velocity is a vector, you can have an acceleration just by changing the direction of the velocity. Moving in a circle at a constant speed means there is indeed an acceleration.

If we have an object moving in a circle, the acceleration is pointed towards the center of the circle and depends on two things: the angular velocity (ω) and the circular radius (r). If you increase either of these values, the magnitude of the acceleration will also increase according to the following:

So perhaps you can see where this is going. If I move a phone around in a circle, I can measure both the acceleration and the angular velocity. From this, I can calculate the radius of the circle—which will be the distance from the center of the circle to the accelerometer. That shouldn’t be too difficult. Actually, I have done this experiment before but it was a slightly different setup.

Actually, you can do this yourself. Really, all you need a device that rotates the phone such that it moves in a circle with a constant radius. For me, I used this nice rotating platform.

Notice the addition of the ruler so that I can accurately measure the distance from the center of the circle to the bottom of the phone. I also put a small clamp at the end to prevent the phone from flinging off the platform. That would be bad.

The other thing you need is a way to measure both the angular velocity and the acceleration. Most phones have a type of gyroscope to measure rotations so that you can get both measurements with your phone. Although there are several apps to record sensor data on your phone, but I really like PhyPhox (for both Android and iOS).

Now we are all set. Start recording data and rotate the phone. As the angular velocity changes, so does the acceleration (since the radius is fixed). Since the acceleration is proportional to the square of the angular velocity, I can plot acceleration vs. ω22. It should look something like this (hopefully).

It seems to be linear—so that’s good. The slope of this line is 0.14138 meters with an intercept of 0.093 (rad/s)2 (that’s close to zero). That slope is the important part. It’s the distance from the center of the circle to the sensor. I recorded the distance of the bottom of the phone to the center with a radius of 0.09 meters. This means that the accelerometer is 5.1 centimeters above the bottom of the phone.

But wait! What about the side-to-side location? I can repeat the experiment with the side of the phone facing the center of the circle. Here is the data for that run.

In this case, I had the screen facing down with the “sleep” button side of the phone facing the center of the circle at a radius of 15.9 cm. The slope of the line above is 17.7 cm. That means the sensor is 1.8 cm from the side. OK, this is technically wrong, but I’m going to use it anyway. The 17.7 cm is actually the radial distance to the sensor. This will only give me the distance from the side of phone if the sensor was half way from the top of the phone. Oh well, this will be close enough.

So here is a diagram of my iPhone (looking at it from the back).

Pretty sure that’s where the sensor is located. Now I just need to take apart my phone to verify this result. Oh wait. I’m not going to do that.

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Japan has developed an inflatable scooter that weighs practically nothing

The University of Tokyo engineers have developed the Poimo inflatable electric scooter, which is created individually for each owner. It is enough to send your photo to the manufacturers – and a personal optimized model will be assembled for you.

The scooter is designed with a special program for the body size of a particular user and his specific fit. Moreover, each owner is free to make any changes to this model. If he makes any changes to the drawing, the program will automatically redesign the electric bike to maintain its strength, stability and controllability. When the model is finished and approved, it is handed over to the manufacturer.

Scooter Poimo

The scooter consists of seven separate inflatable sections that are constructed from durable fabric and sewn with straight stitch. It remains to add electronic components – in particular, a brushless motor and a lithium-ion battery. 

The finished electric scooter weighs about 9 kg and can travel at speeds up to 6 km / h (that is, slightly faster than a pedestrian). It can work for an hour on one charge.

This is how the current version of Poimo looks like in action:

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Excerpts from Elon Musk’s speech at the Martian Society convention

Elon Musk’s comments with questions relayed from the Mars Society Membership by Dr. Robert Zubrin, James L. Burk, and Carie Fay. Following Elon’s 30 min time, Dr. Zubrin took additional questions. This special event was part of the 2020 Mars Society Virtual Convention from October 14-18, 2020.

About Starship Test Schedule:

– entering orbit – with a probability of 80% -90% will take place in 2021

– the probability of the return of the ship and the 1st stage in this flight is 50%

– test of refueling in orbit – 2022

– Starship lunar version – 2022 or 2023

– Starship flight to Mars – around 2024

The goal of the Starship is to build a self-sufficient settlement on Mars as quickly as possible. Musk does not rule out the possibility that this will not be achieved during his lifetime. According to his rough estimates, to create a self-sufficient city, it will be necessary to deliver 1 million tons of cargo, which corresponds to 4-5 million tons in a low Earth orbit. Modern single-use launch vehicles are capable of removing less than 1% of this value.

“Disposable launch vehicles are completely stupid. They are a waste of time. I think people need to stop wasting time on this. If you try to sell a disposable plane, you will be thrown out of the office. If you try to sell a disposable car, you will also be thrown out of the office. “

A series of questions and answers followed:

What is the best landing site on Mars?

– I’m not sure about that. But I can name the criteria. The first of these is latitude: most likely it will be in the northern hemisphere, far enough to the north to have water ice, but to still have enough sunlight.It also needs to be low to get the most benefit from atmospheric braking.

How do you prioritize mission priorities: research, infrastructure construction, and science?

– The first will be the construction of a fuel plant.

A question from a teenager who wants to become an engineer and robot maker with a dream to work at SpaceX: what is the most important education in order to become an engineer?

– There are many varieties of this profession: you can be an aerospace engineer, in the field of electronics, software, or a chemical engineer involved in creating safe production of fuels. I think physics is a good foundation for critical thinking.

Boring Company was originally conceived as a tunnel manufacturing firm on Mars?

– No. It was originally something of a joke. I thought tunnels were a good solution to reduce the traffic problem in cities and improve the quality of life by turning parking lots into green parks. To do this, you need to go to 3d [get away from the “flat” infrastructure – approx. per.]. I think tunnels are good for Mars too. But there you need a lot lighter equipment: you don’t care about mass on Earth, but you will have to take care of it a lot when going to Mars.

At Boring Company, have you learned a lot of technology that might come in handy on Mars?

– I think, yes.

Do you have any tips for young people who love Mars but don’t know how to participate in its settlement?

– I think any strong advocate of the need to conquer Mars matters. People often don’t even think about it. I often talk to people who don’t even know about it. Therefore, I consider it important for humanity and consciousness in general to bring a discussion about this to society. Talking about it with friends and acquaintances – I think this is what we should do. In my estimate, we will spend less than 1% of our efforts on Mars exploration, exactly less than healthcare, perhaps even less than cosmetics – this will be enough to make life multi-planetary. But this requires people to start talking about it 100 times more often. I think this is what really matters. [the entire cosmonautics of the world is $ 424 billion a year, while cosmetics is $ 532 billion, and tobacco production is $ 849 billion – approx. per.]

What’s the coolest part about Starship development?

– I think the coolest detail is the ability to work with a great group of engineers and come up with interesting solutions. I think the best thing is the opportunity to work with smart and creative people who come up with solutions that were not available before. This is a great reward.

What do you focus on when hiring, especially with regard to engineers?

“We’re looking for signs of exceptional ability. Or at the very least, striving to do exceptional things at SpaceX.

Are you planning to make a Mars-Earth communication system like Starlink?

– Yes, I think we will use a laser, probably launched into orbit, to avoid atmospheric diffraction. Thus, it will be a laser beam going from the orbit of the Earth to the orbit of Mars. And also relay satellites in solar orbit, since the laser beam cannot be sent through the Sun [when it is between Mars and Earth – approx. per.].

Can Starship be used for other destinations like Venus and other planets?

– Starship will be able to travel to any target in the solar system that has a solid surface when fuel depots appear. It is not the kind of transport that will take us to other stars, but when we become a multi-planetary species, we will create a demand for innovation in space travel that will ultimately lead us to interstellar travel.

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Cern Scientists Plan an Impressive Experiment – They Will Come Into A Parallel Universe

Cern scientists are once again preparing to impress the entire planet and become the focus of discussions with the new experiment they are planning.

An experiment that, if it brings the fascinating result that scientists have in mind,  will change the way we think about the world , will take place in the next few days at the Large Hadron Collider, the European nuclear center, Geneva CERN Research.

The astonishingly LHC complex, the largest, most energetic elemental accelerator in the world,  will be “fired” for the first time to its highest energy levels, in an effort to detect – or even create – tiny black holes. 

If it succeeds, then, a completely new universe will be revealed – rewriting not only the books of physics, but also the books of philosophy! 

It is possible, however,  that gravity from our universe will “leak” into this parallel universe, as LHC scientists say. 

From the Higgs boson to dark matter and the parallel universe

According to the British Express, the experiment is sure to “trigger” the critics, who are worried about the LHC, many of whom warn that the elementary particle accelerator will mark the end of our universe, creating a of the black hole.

Nevertheless,  Geneva has remained … intact since 2008, when the LHC began its spectacular “work”.

The first scientists at the Large Hadron Collider proved the existence of the Higgs boson – a key building block of the universe – and the LHC appears to be on track to locate “dark matter” – a previously undetectable force now considered that it constitutes the majority of matter in the universe, being, in fact, the reason why the latter is constantly expanding and moving away. 

So next week’s experiment is considered to change the game. 

The truth is out there

Mir Faizal, one of three heads of the three natural groups behind the experiment, said: 

“Like many parallel sheets, which are two-dimensional objects (width and length) can exist in a third dimension (height) , so parallel universes can also exist in higher dimensions. We anticipate that gravity can leak into extra dimensions, and if that happens, then tiny black holes can be produced in the LHC. 

Normally, when people think of the multiverse, they think of the interpretation of quantum mechanics by many worlds, where every possibility is realized. This cannot be tested and so it is a philosophy and not a science. We do not mean this with parallel universes. What we mean is real universes, in extra dimensions. The truth is out there.”

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