Answer:
I haven't learnt physics at all yet but I'll try.
After the two cars collide, they move at 6 m/s.
This tells us that the 2nd car which collided with the first car which is 2000 kg is much heavier than the 1st one, if the second one was lighter, the two cars coupled together speed would be much more than just 6 m/s.
Refer to explanation for working.
Explanation:
Now find out how much g or kg is the 2nd car more than the 1st.
2000 ÷ 10 = 200 (I don't really know how to explain this part)
10 - 6 = 4 (Difference for 1st car average speed per second and the coupled cars average speed per second)
200 x 4 = 800
2000 + 800 = 2800 kg
(Final answer)
