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E = mc2
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- Lemon Slice
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E = mc2
E = energy (measured in joules, J)
m = mass (measured in kilograms, kg)
c = the speed of light (measured in metres per second, ms ), but this needs to be "squared".
m = mass (measured in kilograms, kg)
c = the speed of light (measured in metres per second, ms ), but this needs to be "squared".
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- Lemon Quarter
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Re: E = mc2
panamagold wrote:E = energy (measured in joules, J)
m = mass (measured in kilograms, kg)
c = the speed of light (measured in metres per second, ms ), but this needs to be "squared".
So why do I feel I have less energy since I have put on some extra mass?
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- Lemon Half
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Re: E = mc2
jfgw wrote:panamagold wrote:E = energy (measured in joules, J)
m = mass (measured in kilograms, kg)
c = the speed of light (measured in metres per second, ms ), but this needs to be "squared".
So why do I feel I have less energy since I have put on some extra mass?
I think it is all relative.
John
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- Lemon Half
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Re: E = mc2
panamagold wrote:
c = the speed of light (measured in metres per second, ms ), but this needs to be "squared".
That bit has always 'bothered' me
What is a velocity squared?
It's definitely not a velocity.
10km/s = 6 miles/s approx
100km/s is not 36 miles/s
Re: E = mc2
in the equation E = mc^2
it is equating the dimensions of Energy (Joules) to mass (kg) x speed (m / s) x speed (m / s)
so the units of 'c^2' are m^2 / s^2 (not just m/s)
so, in your example 100km^2 / s^2 is analogous to 36 miles^2 / s^2
-Dom
it is equating the dimensions of Energy (Joules) to mass (kg) x speed (m / s) x speed (m / s)
so the units of 'c^2' are m^2 / s^2 (not just m/s)
so, in your example 100km^2 / s^2 is analogous to 36 miles^2 / s^2
-Dom
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- Lemon Half
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Re: E = mc2
It's always bothered me why it isn't E = (mc2)/2 like the equation for kinetic energy E= (mv2)/2
When I asked my physics teacher as a child I was fobbed off with because c is so large it doesn't matter about the 1/2.
Regards,
Percol
When I asked my physics teacher as a child I was fobbed off with because c is so large it doesn't matter about the 1/2.
Regards,
Percol
Re: E = mc2
Percol351 wrote:It's always bothered me why it isn't E = (mc2)/2 like the equation for kinetic energy E= (mv2)/2
When I asked my physics teacher as a child I was fobbed off with because c is so large it doesn't matter about the 1/2.
Regards,
Percol
E=mc^2 and the Newtonian Kinetic Energy equation are showing two different things.
The Newtonian equation for Kinetic Energy is E(k) = (m/v^2) / 2
The Relativistic equation for Kinetic Energy is E(k) = E(total energy) - E(rest energy)
E(k) = mc^2 / sqrt(1 - (v^2 / c^2) ) - mc^2
At low speeds (ie v << c) we can approximate this using the first two terms of a Taylor expansion for a reciprocal square root
E(k) ~ mc^2 (1 + v^2 / 2c^2) - mc^2 ~ (mv^2)/2
which is the Newtonian equation, i.e. at low speeds, relative to the speed of light, the Newtonian equation is a good approximation of the Relativistic equation.
-Dom
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- Lemon Slice
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Re: E = mc2
psychodom wrote:
E=mc^2 and the Newtonian Kinetic Energy equation are showing two different things.
The Newtonian equation for Kinetic Energy is E(k) = (m/v^2) / 2
The Relativistic equation for Kinetic Energy is E(k) = E(total energy) - E(rest energy)
E(k) = mc^2 / sqrt(1 - (v^2 / c^2) ) - mc^2
At low speeds (ie v << c) we can approximate this using the first two terms of a Taylor expansion for a reciprocal square root
E(k) ~ mc^2 (1 + v^2 / 2c^2) - mc^2 ~ (mv^2)/2
which is the Newtonian equation, i.e. at low speeds, relative to the speed of light, the Newtonian equation is a good approximation of the Relativistic equation.
-Dom
Wow....I am not worthy!
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