Final answer:
The resultant force acting on Box A, which is being pushed with a horizontal force of 30 N and has no other forces mentioned, is b. 3 N.
Step-by-step explanation:
The question asks us to find the resultant force acting on Box A, which has a mass of 10 kg and is being pushed with a horizontal force of 30 N. To calculate the resultant force on Box A, we need to consider all the forces acting on it. If Box A is on a horizontal surface without any mention of friction or other forces and Box B remains at the same position, then the only force acting on Box A is the applied force of 30 N. Therefore, the resultant force acting on Box A is indeed 30 N. It's important to note that if there were other forces, such as friction or air resistance, these would have to be taken into account in the calculation. Since the question does not provide details about such forces, the answer is the initial applied force.
The resultant force acting on Box A can be found by subtracting the force of friction from the applied force. Since Box B stays at its position, it does not exert any force on Box A. So, the force of friction experienced by Box A is equal to the force required to keep it at rest, which can be calculated using the formula F = mass x acceleration. In this case, the mass of Box A is 10 kg and the acceleration is 2 m/s². Therefore, the force of friction is 20 N. So, the resultant force acting on Box A is 30 N - 20 N = 10 N.