Answer:
Mercury / Mars
Explanation:
For an object launched straight upward, the following SUVAT equation can be used
where
v is the final velocity
u is the initial velocity
g is the acceleration of gravity (free fall acceleration) (the negative sign is due to the downward direction of gravity)
h is the maximum height reached
At the maximum height, the velocity is zero, so v = 0. Re-arranging the equation,
So we see that for equal initial velocity (u), the maximum height reaches is inversely proportional to the acceleration of gravity. Therefore, the potato gun will reach the highest altitude in the planets with lowest acceleration of gravity, therefore Mercury and Mars (3.7 and 3.6 m/s^2).