A weightlifter lifts a barbell above her head. Is there work done on the barbell?

Yes

Explanation:

The work done on a body relies upon the force, displacement, and the angle made between the force and the displacement.

Here, the force acting on the barbell is vertically downwards while the vertical displacement is in the upward direction. The angle made between the force (weight) and the displacement is Thus, a work will be done on the barbell by its weight.

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg