Question

A 0.080Kg robin, perched on a power line 6 m above the ground , swoops down to snatch a worm from the ground and then returns to an 8 m high tree beach with his catch. By how much did the birds PE increase in his trip from the power line to the branch?

Answer 1

If the initial PE is mgh(initial) and the final PE is mgh(final) then mgh(initial)-mgh(final) should give you your change in PE.
So, without conversions your answer should be
[(.08)(9.8)(8)]-[(.08)(9.8)(6)]=change in PE which is 1.568Joules.