For the law of conservation of energy, the work done by the teeth must be equal to the variation of mechanical energy of the object. However, there is no variation of the kinetic energy K of the object, because the velocity is constant, and so K is constant as well. So the work done is simply equal to the gravitational potential energy acquired by the object, which is equal to:
[tex]U=mg\Delta h[/tex]
where m=281.5 kg is the mass of the object, [tex]g=9.81 m/s^2[/tex] is the gravitational acceleration and [tex]\Delta h=17.1 cm=0.171 m[/tex] is the height at which the object has been lifted. Using these data, we find:
[tex]U=(281.5 kg)(9.81 m/s^2)(0.171 m)=472.2 J[/tex]
And as we said above, this coincides with the work done by the teeth.
