- #1

simphys

- 324

- 46

- Homework Statement
- Determine the escape velocity from the Sun for an

object (a) at the Sun’s surface (##r=7E5km, M=2E30kg##)

and (b) at the average distance of the

Earth(##1.5E8km##) Compare to the speed of the Earth

in its orbit.

- Relevant Equations
- ##U = -GM_Sm/r_S##

hello guys, sims back again with another question..

I don't understand what is up with question (b)

cuz like.. to get ##v_esc## we assume that at ##r_0=\inf## ##v=0## but now if I assume at ##r=1.5E8## that ##v=0##.

And then find ##v_esc## from the following:

##\frac12*mv_{esc}^2 - \frac{GM_Sm}{r_S} = GM_Sm/r_0## is not correct?

HOWEVER IN THE~~STUPID ~~SOLUTIONS IT SAYS THAT IT'S FOUND AS IF IT'S THE Escape velocity as is written for the sun but with ##r_0## instead of ##r_S##

i.e. ##v_{esc} = \sqrt{2GM_S/r_0}##

What I don't understand is... why?

Note: I am not acquainted with kepler's laws, not covered at univ (engineering) but I'll look into it myself a bit later.

I only know the ##U_grav## and ##F_grav## and that's about it.

I don't understand what is up with question (b)

cuz like.. to get ##v_esc## we assume that at ##r_0=\inf## ##v=0## but now if I assume at ##r=1.5E8## that ##v=0##.

And then find ##v_esc## from the following:

##\frac12*mv_{esc}^2 - \frac{GM_Sm}{r_S} = GM_Sm/r_0## is not correct?

HOWEVER IN THE

i.e. ##v_{esc} = \sqrt{2GM_S/r_0}##

What I don't understand is... why?

Note: I am not acquainted with kepler's laws, not covered at univ (engineering) but I'll look into it myself a bit later.

I only know the ##U_grav## and ##F_grav## and that's about it.

**Thanks in advance**