Answer:
The velocity of the car of mass 4 kg with respect to ground is 0 m/s
Explanation:
The problem initially stated that the car is at rest. at this stage, the velocity of the car relative to the ground is already = 0 m/s.
When the 10 kg car began to move, the problem did not specify at any point that the 4 kg car began to move also. Hence, the motion of the 10 kg car did not affect the 4 kg car in any way.
As a result, relative to the ground, the velocity of the 4 kg car is still 0 m/s since no motion was recorded by the car.