(a)[2]
Using the definition of gravitational potential, explain why gravitational potential has a negative value.
(b)
(b(i))[3]
From Fig. 1.2, determine the change in kinetic energy of the rock as it travels from the location where $x = 0.1 \times 10^{12}\,\text{m}$ to the location where $x = 1.2 \times 10^{12}\,\text{m}$. Say whether the change is an increase or a decrease.
(b(ii))[3]
At $x = 0.1 \times 10^{12}\,\text{m}$, the rock has speed $v$. Find the smallest value of $v$ for which the rock can reach the point where $x = 1.2 \times 10^{12}\,\text{m}$.