Complete question:
At a particular instant, an electron is located at point (P) in a region of space with a uniform magnetic field that is directed vertically and has a magnitude of 3.47 mT. The electron's velocity at that instant is purely horizontal with a magnitude of 2×10⁵ m/s then how long will it take for the particle to pass through point (P) again? Give your answer in nanoseconds.
[<em>Assume that this experiment takes place in deep space so that the effect of gravity is negligible.</em>]
Answer:
The time it will take the particle to pass through point (P) again is 1.639 ns.
Explanation:
F = qvB
Also;

solving this two equations together;

where;
m is the mass of electron = 9.11 x 10⁻³¹ kg
q is the charge of electron = 1.602 x 10⁻¹⁹ C
B is the strength of the magnetic field = 3.47 x 10⁻³ T
substitute these values and solve for t

Therefore, the time it will take the particle to pass through point (P) again is 1.639 ns.
The velocity of an electron that has been accelerated through a difference of potential of 100 volts will be 5.93 *
m/s
Electrons move because they get pushed by some external force. There are several energy sources that can force electrons to move. Voltage is the amount of push or pressure that is being applied to the electrons.
By conservation of energy, the kinetic energy has to equal the change in potential energy, so KE=q*V. The energy of the electron in electron-volts is numerically the same as the voltage between the plates.
given
charge of electron = 1.6 ×
C
mass of electron = 9.1 ×
kg
Force in an electric field = q*E
potential energy is stored in the form of work done
potential energy = work done = Force * displacement
= q * (E * d)
= q * (V) = 1.6 ×
* 100
stored potential energy = kinetic energy in electric field
kinetic energy = 1/2 * m * 
= 1/2 * 9.1 ×
* 
equation both the equations
1/2 * 9.1 ×
*
= 1.6 ×
= 0.352 *
m/s
= 35.2 * 
= 5.93 *
m/s
To learn more about kinetic energy in electric field here
brainly.com/question/8666051
#SPJ4
Edit: You do mean Ridge?
Rocks near Mid-Ocean Ridge are younger than rocks near the trenches.
Seismic data shows oceanic crust is sinking into the mantle at the trenches.
Matching bands of magnetic rock are found on either side of the Ridge. Earth's magnetic fields change these bands over time.