# Another physics question

• Oct 25th 2007, 11:34 AM
beetz
Another physics question
Gold atom has mass of 3.3 * 10^-25 kg and is at rest. It emits an alpha particle of mass 6.6 * 10^-27 kg. As the alpha particle is emitted, teh gold atom becomes an iridium isotope (assume this mass is difference of mass of gold atom adn that of the alpha particle). Alpha particle has speed of 3.4*10^6 m/s.

Find the speed of the iridium isotope after emission process.

hmmm......equation?
• Oct 25th 2007, 01:52 PM
CaptainBlack
Quote:

Originally Posted by beetz
Gold atom has mass of 3.3 * 10^-25 kg and is at rest. It emits an alpha particle of mass 6.6 * 10^-27 kg. As the alpha particle is emitted, teh gold atom becomes an iridium isotope (assume this mass is difference of mass of gold atom adn that of the alpha particle). Alpha particle has speed of 3.4*10^6 m/s.

Find the speed of the iridium isotope after emission process.

hmmm......equation?

Conservation of linear momentum! Before distintegration momentum is zero

So after the momentum of the iridium is in the oposite direction to that of
the alpha particle and of the same magnitude, so:

$\displaystyle v_i \times 3.24~10^{-25}= 3.4~10^6 \times 6.6 ~ 10^{-27}$

where $\displaystyle v_i$ is the speed of the iridium atom.

RonL