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?
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.