- #1
physgirl
- 99
- 0
i don't quite get Newton's third law... :(
It sounds simple enough, F12 = -F21. However, I'm getting that mixed up with the second law now (ie. if there is a net F on the system, there will be acceleration).
For instance, say that there's a box, and the "F" vector is pointing to the right. However, there's another force (say, F2) pointing to the left. If F is greater than F2, then the box will accelerate to the right according to F-F2=ma. Correct?
But... doesn't the Third law say that for any force acting on this box, there's always another "force" (opposite in sign, equal in magnitude) ALSO acting on the box? As in... in the above scenario, there's -F acting upon the box to counter F, and -F2 acting upon the box to counter F2... This confuses me, because this is implying that there's no net force on the system right? Because by the Third law, there's some force (-F21) canceling out the force in interest (F12)?!
Where's my misunderstanding coming from?
Thanks in advance for any input :)
It sounds simple enough, F12 = -F21. However, I'm getting that mixed up with the second law now (ie. if there is a net F on the system, there will be acceleration).
For instance, say that there's a box, and the "F" vector is pointing to the right. However, there's another force (say, F2) pointing to the left. If F is greater than F2, then the box will accelerate to the right according to F-F2=ma. Correct?
But... doesn't the Third law say that for any force acting on this box, there's always another "force" (opposite in sign, equal in magnitude) ALSO acting on the box? As in... in the above scenario, there's -F acting upon the box to counter F, and -F2 acting upon the box to counter F2... This confuses me, because this is implying that there's no net force on the system right? Because by the Third law, there's some force (-F21) canceling out the force in interest (F12)?!
Where's my misunderstanding coming from?
Thanks in advance for any input :)