Question
<p>The positron is a particle with the same mass as an electron but charge <img src="http://session.masteringphysics.com/render?tex=%2Be" alt="+e" align="middle" />. A positron in a bubble chamber moves perpendicular to a <span>3.4</span> <img src="http://session.masteringphysics.com/render?units=T" alt="T" align="middle" /> magnetic field.If the positron’s kinetic energy is <span>28</span> <img src="http://session.masteringphysics.com/render?units=eV" alt="eV" align="middle" />, what’s the radius of its trajectory in the bubble chamber?</p>
Explanation / Answer
The positron is a particle having same mass as electron m = 9.31*10^-31 kg magnetic field is B = 3.4 T kinetic energy is K.E = 28 eV K.E = 1/2 mv^2 28*1.6*10^-19 J = 1/2 *9.31*10^-31 kg * v^2 speed of the particle is v = 3.10*10^6 m/s radius of the chamber is r = mv / q B = 9.31*10^-31 kg * 3.10*10^6 m/s / 1.6*10^-19C * 3.4 T = 5.29*10^-6 m