LAW OF CONSERVATION OF MOMENTUM

Conservation of Momentum

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 the 222 µ, what speed does the original alpha particle have when it is emitted?

No need to convert mass to kg. Why?

Before

Original nucleus = mass = 222 µ,

v = 420 m/s

After

alpha particle = mass of 4.0 µ

v = ?

New Nucleus = 218 µ (alpha lost)

v = 350 m/s

Speed of original alpha particle have 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

Recoil Problems