Two identical objects in outer space have a head-on collision and stick together. if, before the collision, one had been moving at 2 m/s and the other at 1 m/s, their combined speed after the collision would be?

1.5 m/s

Explanation:

Momentum is conserved and conservation of momentum is

p₁ + p₂ = p'₁ + p'₂

or

m₁v₁ + m₂v₂ = m₁v'₁  + m₂v'₂

In our problem, after collision v'₁ will be equal to v'₂.

Since objects are identical m₁ = m₂

m(v₁+ v₂) = 2m x v'₁

(2m/s + 1m/s) = 2v'₁

v'₁ = v'₂ = 1.5 m/s

i think the answer is a, hope this is right, that would be my best guess.