Final answer:
The magnitude of the pull force required to move a 14 kg desk against a 27 N frictional force is 27 N, which is option A. This is based on Newton's second law for objects moving at constant velocity.
Step-by-step explanation:
The question asks for the magnitude of the pulling force required to move a desk that is subject to a frictional force of 27 N. To maintain constant velocity or to move the desk at a constant speed along rough ground, the pulling force must be equal to the force of friction, assuming there are no other forces acting on the desk and we're considering horizontal motion only.
Therefore, the magnitude of the force of the pull required to move the 14 kg desk is 27 N, which corresponds to option A. This can be concluded from applying Newton's second law of motion, which in its simplest form for horizontal motion states that if an object moves at constant velocity, the net force acting on it is zero. Therefore, the pull force must be equal and opposite to the frictional force to achieve this condition.