Using the provided graph, determine the relationship between the square of the period and the mass by calculating the slope.

The graph plots "Square of Period (s squared)" on the y-axis against "Mass (kg)" on the x-axis. We select two points that lie on the drawn line and are easy to read from the grid.
Let's choose:
Point 1: $(x_1, y_1) = (0.0 \text{ kg}, 0.1 \text{ s}^2)$
Point 2: $(x_2, y_2) = (0.5 \text{ kg}, 2.1 \text{ s}^2)$