Question

to what height should an object of mass 2 kg be rise so that its potential energy is 980 Joule

Answer 1

Here's what you are looking for,

                            formula of potential energy is mgh and in the question we are provided with the values of mgh=980J, m=2kg, and g=9.8/10 m/s^2 depending on the question.

                                              mgh = 980

                                              (2)*(10)(h) = 980

                                              h = 980/20

                                              h = 49m ( or 50m if g = 9.8 m/s^2 )