bATo76, Donator
Det var en användare på Reddit i r/theydidthemath som skrev så här:
"Calculating the force generated by a solenoid magnetic field is very, very complicated, particularly for extremely powerful ones. But let's look at it from the other direction:
A metal-core plug will be on the heavier side. 0.15kg seems to be a good average. The average male torso depth is ~0.25m, so let's say that's the distance over which it can accelerate while staying inside of him. And of course the speed of sound is ~343 m/s.
Using the plug's starting location and velocity as 0, we know that:
x = 0.5at2
and
v = at
This gives us:
0.25 = 0.5at2 =>
0.5 = at2
and
343 = at
With two equations and two unknowns, we can solve for a and t:
343 = at =>
a = 343/t
0.5 = at2 =>
0.5 = (343/t)t2 =>
0.5 = 343t =>
t ~= 0.0014577s
a ~= 343/0.0014577 =>
a ~= 235302.188 m/s2
From that we can calculate the force exerted on the plug using:
F = ma =>
F ~= 0.15*235302.188 =>
F ~= 35295.328N
Most MRIs use either a 1.5T or a 3T magnet, but they currently range from 0.5 to 7. This video shows experimentation with a 4T MRI: https://youtu.be/6BBx8BwLhqg
At the end they are using a pull-meter to measure the force of the magnet. It is hitting ~500lb for a small piece of metal hardware and ~2000lb for an office chair at the mouth of the MRI, which are equivalent to ~2225N and ~8900N respectively. Magnetic pull strength of solenoids is related to the mass of the metal being pulled and inversely related to distance from the center of the field, which would be less for the plug than either object in the video. Given the results in the video and that all of the estimates I used were fairly conservative, it seems highly unlikely that an MRI would exert enough pull strength to accelerate a plug to the speed of sound inside of someone."
Så, om man inte räknar med patientens vrål, kommer den inte upp i ljudets hastighet...
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