Calculating Kinetic Energy of an Alpha Particle

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SUMMARY

The discussion focuses on calculating the kinetic energy of an alpha particle, specifically addressing a misunderstanding regarding the application of Einstein's equation, E = mc². The user initially calculated the energy based solely on the rest mass of the alpha particle, yielding 0.0579 joules, while the correct kinetic energy is 1.89 x 10^-13 joules. The key takeaway is that the total energy of the alpha particle includes both its rest mass energy and kinetic energy, necessitating a separate calculation for kinetic energy.

PREREQUISITES
  • Understanding of Einstein's equation E = mc²
  • Knowledge of alpha particle mass (0.66466 x 10^-26 kg)
  • Familiarity with energy units (electronvolts and joules)
  • Basic principles of kinetic energy calculation
NEXT STEPS
  • Learn how to calculate kinetic energy using the formula KE = 0.5mv²
  • Study the concept of total energy in particle physics
  • Explore the relationship between mass and energy in different contexts
  • Investigate the properties and behavior of alpha particles in nuclear physics
USEFUL FOR

Students studying physics, particularly those focusing on nuclear physics and energy calculations, as well as educators seeking to clarify concepts related to kinetic energy and mass-energy equivalence.

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Homework Statement

attachment.php?attachmentid=65090&stc=1&d=1387977546.jpg

could you help me for the question b?

Homework Equations


E = mc^2

The Attempt at a Solution



the mass of the alpha particle is 0.66466 x 10^-26 kg >> 4.022 u

put it into the equation, so
E = 4.022 x c x c = 3.615 x 10^17 eV >> 0.0579 joule

my answer is that, but my teacher answer is 1.89x10^-13 joule..

which one is true? can you show me where's my wrong?
 

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Merry Xmas.

What you're calculating is the energy due to the (rest) mass of the alpha particle. That's not kinetic energy.

The alpha particle's total energy comprises energy due to its (rest) mass plus its kinetic energy. You need to determine the latter.

You can just work with mass, because mass and energy are basically equivalent (or proportional, depending on choice of units). Calculate the total mass of on the left hand side. Calculate the total mass on the right hand side. You may ignore the photon because at the minimum KE of the alpha particle, the photon will have no energy. Can you now figure out the "extra" mass on the LHS? Convert that to energy.
 
merry christmas too ;)

thankyou :D i understand it now!
 

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