Answer:
m = 0.51[kg]
Explanation:
Potential energy is defined as the product of mass by gravity by height.
[tex]E_{pot}=m*g*h[/tex]
where:
Epot = potential energy = 15 [J]
m = mass [kg]
g = gravity acceleration = 9.8 [m/s²]
h = elevation = 3 [m]
Now replacing:
[tex]E_{pot}=m*g*h\\15=m*9.8*3\\m = 0.51[kg][/tex]