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Re: [Phys-l] Relativity Question



In the numerical example posted yesterday, the F=10 N stands for the force in the middle of the compression (at dx=5 cm). Thanks to the teacher who corrercted me in private today.

Ludwik


.
On May 7, 2007, at 11:46 AM, Tom Sandin wrote:


It may also depend whether you consider all forms of potential
energy contribute to mass. Some may allow only certain forms of
potential energy. Some may regard a ball moving down the slope,
losing its potential energy, and hence losing invariant mass.

Alphonsus

It seems to me that the only potential energy that can be used is the
potential energy that belongs to the system being analyzed.

In this case, the ball does not own the gravitational potential
energy, Rather, that potential energy belongs to the earth-ball
system.

Ignoring frictional losses, that decrease in potential energy of the
earth-ball system shows up as an increase in the translational and
rotational kinetic energies of the ball.

Of course, being a relativistic mass proponent, I say the mass of the
ball increases by an amount equal to its total kinetic energy
increase divided by c^2.

As I understand the anti-relativistic mass viewpoint, the mass of the
ball increases by an amount equal to its rotational kinetic energy
divided by c^2 (because in a co-moving frame of reference the ball
has no translational kinetic energy but does have an increase in its
rotational kinetic energy). This increase is one example of a varying
"invariant" mass.

Tom Sandin


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