Answer:
Mass of the body will be = 6 kg
Explanation:
Given:
Mass of an object = 6 kg
Acceleration due to gravity of the planet = 10 
To find the mass of the body on that planet.
Solution:
Mass of the body is defined as the total amount of matter contained in the body.
Thus, mass of a body will always remain constant irrespective of the acceleration due to gravity. This is because it is an independent quantity and does not vary with acceleration due to gravity.
<em>It is the weight of the body that changes with the change in the acceleration due to gravity as it is given by:</em>

where
represents mass of the body and
represents the accelration due to gravity.
Hence, the mass of the given body will remain = 6 kg.
2nd stone time = 13.0/9.8 = 1.33 seconds
distance = 0.5*9.8*1.33^2 = 8.67 meters
1st stone time = 1.33+1.5 = 2.83 seconds
distance = 0.5*9.8*2.83^2 = 39.24 meters
39.24-8.67 = 30.57 meters apart
60 m because that’s the top energy of the roof