Download Name Date Per ______ HW Magnetic and Centripetal Force (Mass

Name _________________________________ Date ___________________ Per _________
HW Magnetic and Centripetal Force (Mass Spec)
1.
Consider the mass spectrometer shown schematically. The electric field between the plates
of the velocity selector is 950 V/m, and the magnetic fields in both the velocity selector
and the deflection chamber have magnitudes of 0.930 T. a) Is the ion a positive or
negative? b) Calculate the radius of the path in the system for a singly charged ion (1.6 ×
10-19 C) with mass m = 2.18 × 10–26 kg if it leaves the velocity selector at a speed of 3.6x10 6
m/s. c) At what distance did the ion travel from the entrance site?
2. A proton (1.60x10-19 C) has a mass of 1.67 × 10-27 kg. After being accelerated through a
potential difference of 250 V, the proton has a velocity of 5.66x10 4 m/s. The ion enters a
magnetic field of 1.3 T, in a direction perpendicular to the field. Calculate the radius of the
ion’s path in the field.
3. One electron is removed from a methane molecule prior to entering the mass spectrometer
shown below. After passing through the velocity selector, the charged molecule has a speed
of 1.0 X 103 m/s. It then enters the final magnetic field region, in which the field is
6.7X10-3T, and follows a circular path. The molecule lands on the detector 5.0cm from the
entrance to the field. Determine the mass of this molecule. (Neglect the mass of the
removed electron).
4. A particle with a +3.2 μC charge and a kinetic energy of 0.020 J is fired into a uniform
magnetic field of magnitude 1.30 T. If the particle moves in a circular path of radius 0.5 m,
determine its mass. (hint: use KE = ½ mv2 to solve for v)
5. A cosmic-ray proton in interstellar space has an energy of 10.0 MeV and executes a circular
orbit having a radius equal to that of Mercury’s orbit around the Sun (5.80 × 10 10 m). What
is the magnetic field in that region of space? (Conversion: 1.6x10-19 J = 1eV)