I’ve been trying to figure out the correct way to approach a specific setup I am developing to test a small crash test.
I developed a rail in which I position an object on top of another (these are fixed between them with suction pressure, lets imagine a suction cup) and I pull one of the objects using springs and at the end this main “car” hits a wall. The top object, on the other hand, should stay attached to the other.
A representation of the setup can be seen here Representation.
What I’ve been trying to understand is the force that the suction mechanism should bear considering the accelerations and forces involved.
Since I can’t measure the time for the crash (and deceleration), I am having a lot of troubles finding a way of calculating the forces involved and can’t really interpret the results because the object should stay attached (at least from the supposed suction force) but it is being thrown and does not stay attached.
Both objects start from rest and are accelerated until the bottom one hits the wall. I have an accelerometer attached that provides me with accelerations at every instant. I know the masses and although I haven’t done it I can infer the velocity at the moment of the crash from the acceleration graph.
I’ve been trying to understand if I can calculate through momentum or if I should somehow approach this using energy equations. I have had this types of problems before and could never reach a conclusion, I feel like I don’t get the concepts deep enough.
Comments
If the object and the wall are both hard objects, the peak acceleration can be extremely high, and very hard to accurately measure because it’s very brief. Can you explain how your accelerometer is reading “every instant”? The instrumentation accels I’ve worked with have a sampling frequency that is well short of infinity.
You need to know the stiffness of the object 2 and wall interface. Otherwise you have to make assumptions and get any answer you like.
However since you have the acceleration (presumably of m2) then the force at the suction cup is simply a2*m1.