- Electricity and Magnetism 79
collision ionization of atoms although both
charges acquire the same kinetic energy
ntv^2 /2 = e (e is the charge of the parti-
cles, and Aq) is the potential difference) in
an accelerating field? Assume that an atom
to be ionized and a particle impinging on
it have approximately the same velocity af-
ter the collision.
3.19. Two small identical balls lying on a
horizontal plane are connected by a weight-
less spring. One ball is fixed at point 0
and the other is free. The balls are charged
identically, as a result of which the spring
length increases twofold.
Determine the change in the frequency
of harmonic vibrations of the system.
3.20. Two small balls having the same mass
and charge and located on the same verti-
cal at heights h 1 and h 2 are thrown in the
same direction along the horizontal at the
same velocity v. The first ball touches the
ground at a distance / from the initial ver-
tical.
At what height H2 will the second ball be
at this instant? The air drag and the effect
of the charges induced on the ground should
be neglected.
3.21. A hank of uninsulated wire consisting
of seven and a half turns is stretched between
two nails hammered into a board to which
the ends of the wire are fixed. The resistance
of the circuit between the nails is deter-
mined with the help of electrical measuringinstruments.
Determine the proportion in which the