J.J. Thomson's m/e Experiment, Help

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J.J. Thomson's m/e experiment involves determining the mass-to-charge ratio of an electron using differential equations influenced by electric and magnetic fields. The equations m(d²x/dt²) + He(dy/dt) = Ee and m(d²y/dt²) - He(dx/dt) = 0 are utilized to derive the cycloidal path of the electron. The correct parametric equations for the cycloid are x = {Em/H²e}(1 - cos([He/m]t)) and y = {Em/H²e}([He/m]t - sin([He/m]t)). A common error noted in the discussion is the omission of the electric field intensity E in the differential equations.

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  • Understanding of differential equations and their applications in physics.
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  • Knowledge of cycloidal motion and its parametric equations.
  • Basic grasp of the principles behind Thomson's experiment and the significance of the m/e ratio.
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SuicideSteve
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Homework Statement



In Thomson's experimental determination of the ratio m/e of the mass to the charge of an electron, in which the electrons were subjected to an electric field of intensity E and a magnetic field of intensity H, the equations

m(d2x/dt2) + He(dy/dt) = Ee , m(d2y/dt2) - He(dx/dt) = 0 ,

were employed. If x=y=dx/dt=dy/dt=0 for t=0, show that the path is a cycloid whose parametric equations are:

x = {Em/H2e}(1 - cos([He/m]t))
y = {Em/H2e}([He/m]t - sin([He/m]t))

The Attempt at a Solution



I have solved the differential equation by substituting 1 for the constants and come out with:
x = 1 - cost
y = t - sint

My problem is I can not figure out how to end up with the constants in the results.

Any help is greatly appreciated,
Thanks.
Steve.
 
Last edited:
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SuicideSteve said:

Homework Statement



In Thomson's experimental determination of the ratio m/e of the mass to the charge of an electron, in which the electrons were subjected to an electric field of intensity E and a magnetic field of intensity H, the equations

m(d2x/dt2) + He(dy/dt) , m(d2y/dt2) - He(dx/dt) = 0 ,

were employed. If x=y=dx/dt=dy/dt=0 for t=0, show that the path is a cycloid whose parametric equations are:

x = {Em/H2e}(1 - cos([He/m]t))
y = {Em/H2e}([He/m]t - sin([He/m]t))

The Attempt at a Solution



I have solved the differential equation by substituting 1 for the constants and come out with:
x = 1 - cost
y = t - sint

My problem is I can not figure out how to end up with the constants in the results.

Any help is greatly appreciated,
Thanks.
Steve.

There is something wrong with your two differential equations, since an "E" appears in the stated solution but is not present in your DEs.

RGV
 
Ray Vickson said:
There is something wrong with your two differential equations, since an "E" appears in the stated solution but is not present in your DEs.

RGV

Sorry, fixed it.
 

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