<< Mentor Note -- OP correctly re-posted schoolwork question in the HH forums; threads merged >> The full question is: The pendulum inside a grandfather clock has a half period of 1.0000s at a location where the magnitude of the local acceleration of gravity is 9.800 m/s^2. The clock carefully is moved to another location at the same temperature and is found to run slow by 89.0s per day. What is the magnitude of the local acceleration due to gravity at the new location? What I have so far: Delta T = dT/dg * delta g -(T/2g) * delta g = (dT/dg) * delta g -(T/2g) = dT/dg From here I am not sure what to do. Is a half period just T/2? Where should I go from here?