題組內容

三、The figure below shows two toy cars on a frictionless surface. Car A, with mass $30\mathrm{kg}$ , initially moves at $2.0\mathrm{m/s}$ parallel to the $x$ -axis. It collides with car B, which has mass $15\mathrm{kg}$ and is initially at rest. After the collision, car A moves at $1.0\mathrm{m/s}$ in a direction that makes an angle $\alpha = 30^{\circ}$ with its initial direction. What is the final velocity of car B?

(a) Before collision