The value of the final speed depends on the mass of the ore.
Let's call m the mass of the ore. We can solve the exercise by requiring the conservation of momentum, which must be the same before and after the ore is loaded.
Initially, there is only the cart, so the momentum is

After the ore is loaded, the new mass will be (1200 kg+m), and the new speed is

. The momentum p is conserved, so it is still 12960 kg m/s. Therefore, we have

and so the final speed is
Kinetic Energy. Energy is transferred from one object to another when a reaction takes place. Energy comes in many forms and can be transferred from one object to another as heat, light, or motion, to name a few. For the blue ball to move to the position of the green ball, energy must be given to the blue ball.
Answer: 161.3
I have a acellus too and got this question correct, so I hope this helps y’all out