The concept used to solve this problem is that given in the kinematic equations of motion. From theory we know that the change in velocities of a body is equivalent to twice the distance traveled by acceleration, in other words:
![v_f^2-v_i^2 = 2ax](https://img.qammunity.org/2020/formulas/physics/college/i9resyotxek3m5iknew2zpvvgwozy06d9r.png)
Where,
Final and initial velocity
a = Acceleration
x = Displacement
For the given case, the displacement is equivalent to the height (x = h) and the acceleration is the same gravitational acceleration (a = g). In turn we do not have initial speed therefore
![v_f^2 = 2hg](https://img.qammunity.org/2020/formulas/physics/college/8fdgxuv43goake3w9h9s6fk4ozf9djfyft.png)
![v_f = √(2hg)](https://img.qammunity.org/2020/formulas/physics/college/tzs992rpnxz7na2xiern1hislwurcaug54.png)
Our values are given as
![h = 70km = 70*10^3m](https://img.qammunity.org/2020/formulas/physics/college/r3t5fkzm04a9i4ubku8hbaj1mh4tniozz4.png)
![g = 2m/s^2](https://img.qammunity.org/2020/formulas/physics/college/v4n9qtkf2l39a29qi3mkl48qjdxsn26gbj.png)
Replacing we have that,
![v_f = √(2hg)](https://img.qammunity.org/2020/formulas/physics/college/tzs992rpnxz7na2xiern1hislwurcaug54.png)
![v_f = √(2(70*10^3)(2))](https://img.qammunity.org/2020/formulas/physics/college/6tzap5l7rzexi689mlywku4dtvylfw5hjr.png)
![v_f = 529.15m/s](https://img.qammunity.org/2020/formulas/physics/college/gf034a11p7qyu7308wafy9k5mcqjb2mfo4.png)
Therefore the speed with which the liquid sulfur left the volcano is 529.15m/s