Answer:
310.5 J
Explanation:
The total work done by Martha is equal to the increase in gravitational potential energy of the package, which is equal to
[tex]\Delta U = mg\Delta h[/tex]
where
(mg) = 45 N is the weight of the package
[tex]\Delta h[/tex] is the increase in height of the package
The package is carried up 3 flights of stairs, each one with a height of 2.3 m, so the total increase in heigth is
[tex]\Delta h = 3 \cdot 2.3 m=6.9 m[/tex]
And so, the work done by Martha is
[tex]U=(45 N)(6.9 m)=310.5 J[/tex]
