Physics

Problem

A rock of mass

m

is moved vertically in four different ways near Earth’s surface. Gravitational potential energy is taken to be zero at the rock’s initial height, and

\Delta U

denotes the change in potential energy in each situation. 1. Lifted upward

3.0\,\text{m}

2. Lowered downward

2.0\,\text{m}

3. Lifted upward

1.5\,\text{m}

4. Lowered downward

4.0\,\text{m}

Rank the four changes (

\Delta U_1, \Delta U_2, \Delta U_3, \Delta U_4

) from greatest (most positive) to least (most negative). a)

\Delta U_3 > \Delta U_1 > \Delta U_2 > \Delta U_4

\Delta U_4 > \Delta U_1 > \Delta U_2 > \Delta U_3

\Delta U_1 > \Delta U_3 > \Delta U_2 > \Delta U_4

\Delta U_1 > \Delta U_3 > \Delta U_4 > \Delta U_2