If my arm would be much more massive than the rest of my body would my body actually move backward instead of my arm forward

[hgfhjgfh]

(I will use abstract approximate 1 dimension positions for example) I mean let's say I stay at position x=0, now I move my arm forward(positive value change), my arm is at position x=5 any my body is still at position x=0 cause friction of my body and ground is much greater than my body movement backward (caused by moving arm forward).

Now let's say my arm weight 100x more than the rest of my body(it is just example), when I try to move my arm forward will instead my body be at position like x=-5(backward movement) and my arm like x=0 (or a very small positive value) ? (It seems a bit strange - I based it on understanding that less massive part moves much more than more massive)

It seems strange because - let's say I weight 100kg and I keep 300kg in my hands(In this example I am very very strong) when I move my arms forward my body gets more backward movement than my arms forward resulting in - instead of just moving my arms I move away from my arms

[Roamer]

Do you walk on your legs or your arms ?

[hgfhjgfh]

Do you know what reaction force is?

[swansont]

If you were on skates, or on some frictionless surface, your body would move backward as you extended your arms. Absent any external force, your center of mass would not begin to move. So if your arms were ridiculously massive, your body would move back a greater distance, maintaining the CoM at a fixed spot.

 

With friction, though, there is an external force. Then you'd have to worry about how fast you were moving your arms and how big the frictional force was.

[md65536]

You can experiment by holding weights. Swing them and your body will sway in the opposite direction. This already happens even without any additional weight. It's not that one part of you moves while the other is fixed; both move, but the massive parts not as much. You can detect slight backward motion of your body when punching forward.

 

Here's an experiment: Stand steady with your back to a wall, as close to touching it as possible. Punch both hands quickly straight forward, and feel the force with which your back pushes against the wall.

Edited August 11, 2014 by md65536