Ex) 12,600 kg railroad car travels on a frictionless surface with a constant speed of 18.0 m/s. A 5350 kg load at rest is dropped onto the car, what will the car's new speed be?

Total momentum before = total momentum after

m₁v₁ = m₂v₂

V₂ = 12.6 m/s

Ex) An atomic nucleus moving at 420 m/s emits an alpha particle in the direction of its motion and the remaining nucleus slows to 350 m/s.

If the alpha particle has a mass of 4.0 µ and the original nucleus has a mass of 222 µ, what speed does the original alpha particle have when it is emitted?

No need to convert mass to kg. Why?

Speed of original alpha particle when it is emitted?

mom nucleus = mom alpha + mom new nucleus

mv = m_av_a + m_nv_n

v = 4.2 x 10³ m/s