Walker, Halliday & Resnick — Center of Mass and Linear Momentum: Problem 70

70 In Fig. 9-61, puck 1 of mass \( m_1 = 0.25 \text{ kg} \) is sent sliding across a frictionless lab bench, to undergo a one-dimensional elastic collision with stationary puck 2. Puck 2 then slides off the bench and lands a distance \( d \) from the base of the bench. Puck 1 rebounds from the collision and slides off the opposite edge of the bench, landing a distance \( 2d \) from the base of the bench. What is the mass of puck 2? (Hint: Be careful with signs.)