Final answer:
The net force in the football practice scenario is 50 N directed toward the defensive line, meaning the players will move in the defensive line's direction, making the correct answer b) 50 N, defensive line moves backward.
Step-by-step explanation:
The question concerns the net force applied by two groups in a football practice scenario and the resulting movement. When the offensive line is applying a force of 100 N and the defensive line is applying a force of 150 N, these two forces are in opposition. To find the net force, we must subtract the smaller force from the larger one, which gives us 150 N - 100 N = 50 N. This means the net force is 50 N in the direction of the defensive line since they are applying the greater force. Therefore, the two players will move in the direction of the defensive line.
So the correct answer is: b) 50 N, defensive line moves backward.
To relate this with a concept of physics, consider the scenario where forces are applied at different directions. If you were to use the graphical head-to-tail method to determine the resultant force on a rugby player being pushed by forces at different directions, you would add the forces vectorially. Similarly, for a situation where the forces are opposite and along the same line, as in the football scenario, you simply subtract the smaller force from the larger one to find the net force and its direction.