I believe the answer is C. Positive, since it is a sustainable plan to use a renewable source hope this helps :)
Answer: potential energy but no kinetic energy
Explanation:
Since the rock is stationary, velocity is zero, therefore no kinetic energy,but there's potential energy because the rock is at rest,
Answer: C. 12.6
Explanation: 2*pi*1.8= 11.304
11.304/0.9= 12.56
