Question

A charged particle leaves the origin with a speed of 3.0×106 m/s at an angle of 35 degrees above
the x axis. A uniform electric field, given by E=E0j exists throughout the region. what is the value of E0 such that the particle will cross the x axis at 1.50cm if the particle is a) electron and b) proton

what do I do for this???

Answer 1

Use Coulomb's law.

Answer 2

so the speed is irrelevant?

Answer 3

No, it determines the time.

Answer 4

if this was a projectile in a gravity field, i am sure you would have no problems with it. it would look like

Gravity field \(\vec g = 0 ~ \hat i -\hat j ~ 9.81~ (ms^{-2})\)

Instead it says:

Electric field \(\vec E = 0 ~ \hat i + \hat j ~ E_o ~ (N/C)\)

but the ideas are all the same.

And you will be using the equations of motion for constant acceleration and that acceleration will be from the same place: \(\vec F = m \vec a \color{red}{= \vec E q} \) simplifying, in the y direction, to \(a = E_o \dfrac{q}{m}\)

[you can ignore the gravity on the charge due to the numbers]

So use the equations of motion for constant acceleration as you normally would.