A proton traveling at 107 m/s collides with a stationary particle and bounces back at 6.0 x 106 m/s. The particle moves forward at a speed of 4.0 x 106 m/s. If the proton has a mass of 1.67 x 10.27 kg, what is the mass of the particle? before 1.67 x 10-27 kg 107 m/s after 1.67 x 10-27 kg 6.0 x 106 m/s 4.0 x 106 m/s 10. A large compressed spring is placed between a 4000 kg railway car and a 6000 ke boxeer at ro​