Answer:
52 km/h
Step-by-step explanation:
When the two trucks move together after collision, the momentum of the system is conserved. The kinetic energy is not conserved. This is inelastic collision
The formula to apply here is :
m₁v₁ + m₂v₂ = {m₁+ m₂} *vf
Given that ;
m₁ = 8 ton ----convert to kg [ multiply by 907.185] =7258 kg
v₁ = 60 km/h
m₂ = 5 tons ------4536 kg
v₂ = 40 km/h
vf = final velocity
Using the values given;
m₁v₁ + m₂v₂ = {m₁+ m₂} *vf
8*60 + 5*40 = {8+5} * vf
480 + 200 = 13 * vf
680 = 13vf
680/13 = vf
52 km/h = vf