Hey - just asking for some help on some electric potential energy questions.

First I used the equation 1/2mv^2 = q(Va-Vb)
so v = sqrt (((2)(25000)(q)) / m )

and Va-Vb = W / q, so q = W/(Va-Vb)
but then i'm stuck and dont know where to go from there since the mass and the charge (q) isnt' given.

So I said that mgh(of a) = 1/2mv^2 (of b)
so (9.8)h = 1/2(42^2), h = 90. That means that the potential difference between A and B is 90?, and point A is at a higher potential since the charge/mass flows TO B FROM A?

This one I'm completely lost. Leme think, so Va-Vb = 320V = W/q (and q = 1300).

So 320V = W / 1300, W = 416,000J? and that just needs to be converted into horsepower?

1. you need the mass and charge of an electron, check it online or your textbook...
2. it didn't say the particle is accelarate under the effect of gravity, mgh is not working in this case, instead you need E=qV=1/2mv^2 where V is your unknown
3. yes, how many joles is a horsepower?

Can anyone help me with number two please? Any other suggestions?

Potential difference between the block's A and B position is 90 correct?
since 1/2mv^2 = mgh
becomes 1/2v^2 = gh
v = 42, g = 9.8, that solves for h = 90. so potential difference = 90?

Can anyone tell me if that's correct and how the charge differs?

It's the same particle for which mass and charge are given. Just plug them in and solve.

The question says nothing about the particle falling from a height. As vincentchan said, the acceleration is only due to electric field... no gravitational field so you don't need mgh.