A \(2.0-\mathrm{kg}\) cart collides with a \(1.0-\mathrm{kg}\) cart that is initially at rest on a low-friction track. After the collision, the \(1.0-\mathrm{kg}\) cart moves to the right at \(0.40 \mathrm{~m} / \mathrm{s}\) and the \(2.0-\mathrm{kg}\) cart moves to the right at \(0.30 \mathrm{~m} / \mathrm{s}\). What was the initial velocity of the \(2.0-\mathrm{kg}\) cart?