Block 1, of mass m1 = 9.90 kg, moves along a frictionless air track with speed v
ID: 2069450 • Letter: B
Question
Block 1, of mass m1 = 9.90 kg, moves along a frictionless air track with speed v1 = 25.0 m/s. It collides with block 2, of mass m2 = 17.0 kg, which moves initially with speed 4.20 m/s, toward the first block. The blocks stick together after the collision. Find the magnitude p_i of the total initial momentum of the two-block system. (Choose the direction of the first block's motion as positive.) Find v_f, the magnitude of the final velocity of the two-block system.( Choose the direction of the first block's motion as positive.) What is the change Delta K = K_{ m final} - K_{ m initial} in the system's kinetic energy due to the collision?Explanation / Answer
initial momentum of the system p_i= 9.9*25 - 17*4.2 = 176.1 kg.m/s conservation of momentum 9.9*25 - 17*4.2 = (9.9+17)V_f V_f =6.55 m/s Total initial KE = .5*9.9*25^2 + .5*17*4.2^2 = 3243.69 Final total Ke = .5(9.9+17)6.55^2 = 577.04 change = 2666.65 J