We know the equation of motion v = u+ at, where v is the final velocity, u is the initial velocity, a is the acceleration and t is the time taken.
In this case Final velocity = -3.1 m/s, negative sign indicates it is pointing downward.
acceleration = - 3.7m/
. Negative means acceleration is towards center of planet Mars.
Time taken = 3 seconds
![v = u + at\\ \\-3.1 = u-3.7*3\\ \\u = 8 m/s](https://img.qammunity.org/2019/formulas/physics/college/qa316hwycjmpbkj9r3w9cqzom0uatg8514.png)
So jumping velocity of Julia = 8 m/s