A 40 kilogram barrel is rolled up a 10 meter long ramp to a height of 5 meters. How much does the barrel weigh?

Hint's the 10 and 5 are not needed.

What's needed is this: Newton (unit) - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Newton_%28unit%29)

and F=ma; A is the acceleration due to gravity.

While you could express the answer in newtons which would be correct unless someone wants the answer in lbs.

It's confusing because lbs is a force not mass. The slug is the unit of mass in the English system.

As it happens, your always seem to be converting incompatible units like a man weighs 150 lbs and in the medical community they will use kg. You have to assume that the 150 lbs is the force on earth.