Question

A crane lifts a 425-kg steel beam vertically upward a distance of 95 m. How much work (in kJ) does gravity do on the beam if the beam accelerates upward at 1.8 m/s2? Neglect frictional forces. Give your answer to 3 significant figures and remember that work can be positive or negative.

Answer 1

the gravitational force is constant over this short distance

the change in gravitational potential energy (work) is ... m * g * h
... the work is negative (against gravity)


FYI ... technically, the answer sig fig is the smallest of the input data
... the distance (h) is only two sig fig