tahmidbro
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9 Data at the back of the examination paper can be used with the formula 'E = c2 'm to
calculate
A the amount of energy in a proton.
B the mass of coal that produces 6 MJ of energy when burnt.
C the energy produced when an electron and a positron annihilate.
D the energy produced when two protons collide.

In the mark scheme, C is the correct answer. Why not D?

In the event when the protons collide, they could also move at the speed of light, c. In that case, there would be a change in mass. So, an energy might be produced. Please tell me if I am wrong, and also why C is the correct answer.

Any help would be highly appreciated! :-)
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Cam3r0n
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'Produced' is a dodgy word altogether so I don't really like this question.

However, here E = mc^2 tells us the energy 'produced' in the form of photons after annihilation; mass is converted to energy (yes I know mass is energy but this is how it meant in the question). When two protons collide, either the two protons carry on, or (perhaps because they have been accelerated near to c so have increased mass, so have increased energy) the collision causes some of their energy to manifest as more particles.

What's produced here is m from other m rather than E from m, so the equation used once and alone does not calculate the energy 'produced'.

Hope this helps.

PS: protons never travel at the speed of light.
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tahmidbro
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I dont get it. Doesnt like charges repel?
Could you please explain why would the two protons carry on?


(Original post by Cam3r0n)
either the two protons carry on,
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tahmidbro
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(Original post by Cam3r0n)
the collision causes some of their energy to manifest as more particles.

What's produced here is m from other m rather than E from m, so the equation used once and alone does not calculate the energy 'produced'.
If some of their energy is used to manifest as more particles, isn't that m from E ?
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tahmidbro
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(Original post by Cam3r0n)
PS: protons never travel at the speed of light.
When you put them into a particle accelerator such as LINAC, they do.
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Goku's Hairbrush
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(Original post by tahmidbro)
When you put them into a particle accelerator such as LINAC, they do.
its physically impossible for anything with mass to travel at light speed, it would require infinite energy
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Goku's Hairbrush
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(Original post by tahmidbro)
9 Data at the back of the examination paper can be used with the formula 'E = c2 'm to
calculate
A the amount of energy in a proton.
B the mass of coal that produces 6 MJ of energy when burnt.
C the energy produced when an electron and a positron annihilate.
D the energy produced when two protons collide.

In the mark scheme, C is the correct answer. Why not D?

In the event when the protons collide, they could also move at the speed of light, c. In that case, there would be a change in mass. So, an energy might be produced. Please tell me if I am wrong, and also why C is the correct answer.

Any help would be highly appreciated! :-)
when protons collide it has nothing to do with their mass-energy relation since neither is being converted to the other, its more to do with momentum and energy. Whereas in annihilation, the rest mass of the matter and antimatter are converted into energy
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Cam3r0n
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(Original post by tahmidbro)
When you put them into a particle accelerator such as LINAC, they do.
They begin to approach the speed of light. Because it is impossible for them to reach it, their mass begins to increase. The speed of light is the speed at which particles of no mass (i.e. photons) travel.
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