Question

An SUV with a mass of 1.80×103 kg is travelling eastbound with a speed of +15.0 m/s,
while a compact car with a mass of 9.00×102 kg is travelling westbound at -15.0 m/s.
The vehicles collide head-on and stick together. What is the speed of the wreck
immediately after the collision, and which way does it move?

Answer 1

m₁v₁ - m₂v₂ =(m₁+m₂)u
u= (m₁v₁ - m₂v₂)/(m₁+m₂)=
=(1.8•10³•15-9•10²•15)/(1.8•10³+9•10²)=
=13500/2700=5 m/s (eastbound)