The conservation of linear momentum for inelastic collision is written as:
m₁v₁ + m₂v₂ = (m₁+m₂)v'
where
v' is the common velocity after collision
We know m₁ = 0.050 kg, m₂ = 0.075 kg and v₂ = 0 (stationary). We don't know v₁ and v'. To solve this the number of unknowns should be equal to the number of independent equations. Since we have 2 unknowns and 1 equation, this is unsolvable. Suppose v₁ = 5 m/s, then v' equals
(0.05 kg)(5 m/s) + (0.075 kg)(0) = (0.05 + 0.075 kg)(v')
Solving for v',
v' = 2 m/s
