the earth pulls down on you. The floor pushes up on you, so you don't move? Two forces not an action reaction?

Question

Hi ok so I have a question. The earth pulls down on you. The floor pushes up on you, so you don't move. Explain why these two forces are NOT an action-reaction pair of forces. THANK YOU, 10 PTS.

Answer 1

Traction or friction and balance keeps you standing. Technically, the floor is not pushing you, it's just in the way.If you stand still,there is no action or reaction.When you take a step you then have your action reaction aided by friction or traction...

Answer 2

Newton's Third Law is the one everyone knows - "For every action there is an equal and opposite reaction" - but few understand. I teach it to my students this way:

"If A puts a force F on B, then B must necessarily put a force -F back on A"

As an earlier contributor stated, you've got two action/reaction pairs going. The Earth pulls down on you, and you pull up on the Earth. The floor pushes up on you, so you push down on the floor. But you tend to only feel the forces ON you - gravity and the floor - rather than the forces produced BY you.

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Answer 3

that is because the action/reaction force is the gravity of the earth pulls you toward the center of the earth, while the gravity of you pulls the earth toward the center of you.

As an action/reaction on the floor, your weight pushes down on the floor, and the floor pushes up back on you.

2 different sets of action/reaction forces that you put together wrong in your initial statement.

Answer 4

In Newtonian mechanics bodies interact.

Each interaction involves exactly two bodies A and B, and exactly two forces Fab and Fba.

Force Fab is exerted by body A on body B.
Force Fba is exerted by body B on body A.
Pair of forces Fab and Fba is called action-reaction pair. According to third law of Newton
Fab = -Fba

Note that forces Fab and Fba belonging to one action-reaction pair act on two DIFFERENT bodies, the former on B and the latter on A.
Both forces described in your question act on the same body (namely on your body). For this reason alone they cannot be action-reaction pair.

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In situation which you describe there are actually two interactions:

Interaction 1:
Bodies involved:
EARTH
YOU
Forces involved (first action-reaction pair):
F-earth-you (The earth pulls down on you, also known as force of gravity mg)
F-you-earth (You pull the earth up)

Interaction 2:
Bodies involved:
FLOOR
YOU
Forces involved (second action-reaction pair):
F-floor-you (floor pushes up on you, also known as normal reaction of the floor N)
F-you-fllor (You push the floor dow, also known as 'weght W')


Forces acting on you must be balanced, becuase your acceleration is zero:
0 = ma = F-earth-you + F-floor-you = mg + N
0 = mg + N . . . . . (1)
Agian, according to third law of Newton action-reaction pair consists of equal and opposite forces:
F-floor-you = -F-you-fllor
N = -W . . . . . . (2)
Combine (1) and (2):
0 = mg - W
mg = W

The last equation means:
your weight W is equal to force of gravity mg.
If you are still with me so far, then it did not escape your attention, that weight and force of gravity are two different forces, acting on two different bodies, but equal as vectors.

Answer 5

Very much, Action reaction. So no need to explain.

Answer 6

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