A) What is the minimum speed, relative to the Sun, necessary for a spacecraft to escape the solar system if it starts at the Earth's orbit?

Question

B) Voyager I achieved a maximum speed of 125 000 km/h on its way to photograph Jupiter. Beyond what distance from the Sun is this speed sufficient to escape the solar system?

so for part A I used the equation...
V(esc)=square root of (2*G*M(earth))/(distance from the earth to the sun) is that right?

and i don't understand how to do the second part.

The escape velocity from Earth's orbit into interstellar space is 42 km/sec.
Source:
http://science.jrank.org/pages/3756/Kepler-s-Laws-Applications-generalized-forms-Kepler-s-laws.html

For you other question try:
http://en.wikipedia.org/wiki/Escape_velocity#Calculating_an_escape_velocity
If no help repost that question and a physics expert probably will get it tomorrow.

On both parts, start with the PE due to Sun

PE= INT Force*dx from inf to r, For the A, r will be Earth orbit radius, and for B), r will be the unknown.

INT GMs*M/r^2 dr= GMs*M/r

Set that equal to 1/2 GMv^2 in the first, with r= rearth orbit.
In Part A) This will change what Mass is in the equation.

In part B)
you know the KE, set that equal to GMs/r and solve for r.