- #1
nate99
- 18
- 0
Hello,
I have seen several explanations on the Internet about how to resolve Newton's Third Law and Unbalanced Forces, but none made sense to me in a way that I really understood it.
Scenario 1:
There is a block on the ground, the ground has friction with say static friction force 10 N. I push the block with 20 N. It moves because there is now an unbalanced force on on the block. The net force on the block is 10 N in the direction I am pushing it.
Force relationship 1: When I push on the block with 20 N, the block is pushing on me with 20 N.
Force relationship 2: Is the block is pushing on the floor with 20 N and the floor is pushing back on the block with 10 N of friction?
In this case for the second relationship, there is an opposite force of the floor pushing on the block, but it is not equal, correct?
How can Newton's Third Law account for unbalanced forces?
Scenario 2:
Maybe a variation on the same type of problem, just need to know how best to think about it and explain it.
One car going fast approaching another car going slow in opposite directions head on. When they collide, I understand that there is an equal and opposite force. Meaning if both had infinite force meters that collided head on, at the moment of impact they would say the same number.
However, one car would probably knock the other out of the way.
Is the best explanation that despite the equal and opposite forces, there is a clear difference in momentum?
Scenario 3:
A projectile is traveling at a constant velocity and hits someone. It will clearly do damage to the person. However, if it is traveling at a constant velocity then there is no acceleration. If there is no acceleration then there is no Force.
Why does it do damage?
Is it because when the projectile strikes something, the equal and opposite forces makes it decelerate over a short span of time? Would that deceleration be used in the F=ma equation to figure out how much force it hits the person with? Does it relate to impulse?
Thank you so much for clearing up these misconceptions in my head, and I hope you won't mind the follow up questions I am sure to have.
I have seen several explanations on the Internet about how to resolve Newton's Third Law and Unbalanced Forces, but none made sense to me in a way that I really understood it.
Scenario 1:
There is a block on the ground, the ground has friction with say static friction force 10 N. I push the block with 20 N. It moves because there is now an unbalanced force on on the block. The net force on the block is 10 N in the direction I am pushing it.
Force relationship 1: When I push on the block with 20 N, the block is pushing on me with 20 N.
Force relationship 2: Is the block is pushing on the floor with 20 N and the floor is pushing back on the block with 10 N of friction?
In this case for the second relationship, there is an opposite force of the floor pushing on the block, but it is not equal, correct?
How can Newton's Third Law account for unbalanced forces?
Scenario 2:
Maybe a variation on the same type of problem, just need to know how best to think about it and explain it.
One car going fast approaching another car going slow in opposite directions head on. When they collide, I understand that there is an equal and opposite force. Meaning if both had infinite force meters that collided head on, at the moment of impact they would say the same number.
However, one car would probably knock the other out of the way.
Is the best explanation that despite the equal and opposite forces, there is a clear difference in momentum?
Scenario 3:
A projectile is traveling at a constant velocity and hits someone. It will clearly do damage to the person. However, if it is traveling at a constant velocity then there is no acceleration. If there is no acceleration then there is no Force.
Why does it do damage?
Is it because when the projectile strikes something, the equal and opposite forces makes it decelerate over a short span of time? Would that deceleration be used in the F=ma equation to figure out how much force it hits the person with? Does it relate to impulse?
Thank you so much for clearing up these misconceptions in my head, and I hope you won't mind the follow up questions I am sure to have.