1. The problem statement, all variables and given/known data The centre of inertia (G) of a heterogeneous vehicle tyre has a distance D=0.1cm from its axis of rotation (the tyre's). The axis is referred to as Delta. The mass of the tyre is M=10kg and its radius is R=20cm. O is the center of the tyre (belongs to the axis) 2. Relevant equations Find the mass of an object (dot) X attached to the tyre so that the centre of inertia G is identical to the axis of rotation. 3. The attempt at a solution This is what I've done so far, but with no avail: I've considered G' as the centre of inertia of the whole group (the tyre and the object X), and G1 as the centre of inertia of X and "m" as its mass. Therefore: Vector OG' = (m*vector OG1 + m*vectorOG) / m + M I substituted G for O since we want it identical to the axis, which results into: Vector OG' = (m*vector OG1 + m*vecto OO) / m + 10 Vector OG' = (m*vector OX) / m + 10 ( G1 = X itself) Thus: OG' = (m*20) / m + 10 But I'm not sure where it's going to lead me. Please help me.