Question

A body of mass m = 110 kg moves along a curved trajectory from a point A at height hA = 3 m above the ground to a point B at a height hB = 4 m. What is the work WAB done by the gravitational force?(assume g = 10 m/s2)
A: WAB = -100J
B: WAB = +100J
C: WAB = -10J
D: WAB = because the gravitational force is conservative
E: WAB = +100J

Answer 1

The work W_AB done by the gravitational force

W_ab=(F ⃗,r ⃗ )=F∙r∙cos⁡α
We have

W_ab=F∙r∙cos⁡α=mg∙(h_B-h_A )∙cos⁡〖180°〗=110∙10∙(4-3)∙(-1)=-1100 J