Not solely do I get the “form” of the acceleration curve for the colliding cart, however I additionally get a most acceleration of –6.67 meters per second squared. With that acceleration and the mass of the cart (0.566 kilogram), we get a most influence pressure of three.73 newtons.
This is not fairly the identical worth I obtained from the pressure sensor—and that is OK. There are two predominant explanation why the utmost pressure is completely different with this technique. First, I’ve solely collected a place level each 1/thirtieth of a second, as a result of my video body charge was 30 frames per second. It is solely potential to extend this body charge, however I saved it at a standard worth as a result of that is what you normally see in actual movies.
The second challenge is that after I calculate the speed after which acceleration, I am truly discovering an acceleration worth for just some factors at a time. This may result in some small errors that put the ultimate worth off a bit bit.
Nonetheless, this video technique is nice. It is noninvasive, and you are able to do it after the very fact. You actually simply want a video. (Figuring out the mass of the article is useful too.)
Accelerometer
In case you do not need to use video evaluation, there’s one other strategy to get the acceleration information (after which use that to search out the pressure). It is potential to only measure the acceleration instantly, and also you in all probability have a tool that may do it with you proper now: It’s referred to as a smartphone. Your cellphone has an accelerometer in order that it may possibly measure the way it strikes, and it’s used for issues like lidar, augmented reality, and even long-exposure photos.
For my part, one of the best app that provides you acceleration information out of your cellphone is PhyPhox. (It is free.) You’ll be able to truly get information from all the sensors in your cellphone with this app, like stress, magnetic subject, and rotation.
However anyway, what occurs if I stick my cellphone on the cart colliding with the barrier? This is the info I get:
Illustration: Rhett Allain
From this, I get a most acceleration of 6.55 m/s2. I can discover the utmost influence pressure once more utilizing the mass of the cart (plus the iPhone, which will increase the mass). This places the biggest pressure throughout influence at 5.32 newtons.
In fact, you possibly can measure acceleration with sensors apart from those in your cellphone. The truth is, nearly each fashionable automotive has some kind of accelerometer that it makes use of to find out when to deploy the airbags: when it senses excessive accelerations throughout influence. You may additionally put different acceleration sensors within the automotive and measure the acceleration of various factors within the automobile. This could produce information that tells you ways the automotive deforms, or strikes relative to itself, throughout a crash.
This is a enjoyable—and protected—experiment you possibly can attempt at residence. Take your cellphone with the PhyPhox app and drop it from very brief distances onto a pillow whereas measuring the acceleration. Subsequent, attempt dropping the cellphone from the identical peak onto one other mushy object to match the influence acceleration. Hopefully, it is best to discover that the softer the touchdown goal, the decrease the worth of acceleration (and thus pressure) throughout influence.
