Physics

Problem

3.0\,\text{kg}

object is moved through the following vertical displacements relative to its initial position: upward

4.0\,\text{m}

, then downward

7.0\,\text{m}

, and finally upward

2.0\,\text{m}

. Taking

g = 9.8\,\text{m/s}^2

, which of the following pairs correctly gives (1) the net change in gravitational potential energy

\Delta U

of the object relative to its starting point and (2) the net work

W_g

done on the object by the gravitational force? a)

\Delta U \approx +29\,\text{J};\; W_g \approx -29\,\text{J}

\Delta U \approx -29\,\text{J};\; W_g \approx +29\,\text{J}

\Delta U \approx -29\,\text{J};\; W_g \approx -29\,\text{J}

\Delta U \approx -88\,\text{J};\; W_g \approx +88\,\text{J}