GS-1 Physical Sciences Question 1

[alistar2005814]

the answer explanation says that choice D is correct because this is the only option that talks about two forces acting on the SAME object in opposite direction. I thought Newton's third law specifically applies to two different objects applying the same force in opposite direction. Can you please correct this discrepancy?

[calena7178147]

The two forces they are talking about here are the Lift Force and the Weight, which do not form an action – reaction pair, and therefore may not be acting on different objects.

The Lift force is the Force of the moving air UPWARDS on the wing, and the Weight of the aircraft, acting DOWNWARDS.

The action – reaction pairs are: Lift Force of air on the wing, and the force of wing on the air and the force of Earth on the wing and the force of wing on the Earth.

The forces on the wing are therefore, Lift force of air on the WING UPWARDS and the Force of Gravity on the WING DOWNWARDS.

Thus, like the option D, these two forces act on the SAME object; the WING, acting in opposite directions; WING UPWARDS, due to Lift exerted by Air and, WING DOWNWARDS, due to Gravity of the Earth.