Final answer:
The net force is 50 N in the direction of the force exerted by the defensive line. A football lineman can still out-push the opponent by applying a greater force, leading to acceleration in his direction. The net force exerted on a rugby player is calculated by the vector sum of the forces applied by his teammates and opponents.
Step-by-step explanation:
The net force applied when the offensive line is applying 100 N of force and the defensive line is applying 150 N of force can be determined by finding the difference between the two forces, since they are opposing each other. In this case, the net force would be 50 N in the direction of the defensive line, i.e., in the direction of the stronger force. This is consistent with Newton's second law, which states that the acceleration of an object is dependent upon two variables – the net force acting upon the object and the mass of the object – with the direction of acceleration being in the direction of the net force.
Regarding the lineman's reasoning mentioned by the student, Newton's third law indeed states that every action has an equal and opposite reaction. However, this does not mean it's senseless to try to out-push the opposing player. If a player exerts a greater force than his opponent, the reaction force will still be equal and opposite, but the net force will not be zero, resulting in acceleration in the direction of the stronger force.
For instance, if a rugby player is being pushed with different forces from multiple players, the net force can be found using vector addition. If two players push him forward with forces of 60 N and 90 N, and two players from the opposing team are pushing him backward with forces of 100 N and 65 N, the net force would be calculated by summing these vectors. The resultant force in this case would be calculated by subtracting the sum of the backward forces from the sum of the forward forces, resulting in a force that either pushes the player forward or backward, depending on which sum is greater.