Added force in a line of people pushing

[pkguy57]

If a person is pushing against a wall with his hands and he has a line of people behing him with their hands on the shoulders of the person in front of them pushing, does the force travel all the way to the wall? This is with a steady pushing force, not a sudden impact force. Would it make a difference if they were body to body instead of hand to shoulder?

 

[Studiot]

Start with one person pushing.

There are two opposing horizontal forces acting, maintaining the equilibrium of that person, considered as a free body.

Reaction from wall = Friction against the ground

Now introduce a second person, pushing in the same direction as the first.
Again consider the free body equilibrium of the first person.

Reaction from wall = Friction + Push from Second Person

R = F + P

 

[xxChrisxx]

Assuming people with rigid arms :P

 

[Danger]

There would be losses all along the line. For instance, there would be almost no difference in effect upon the wall between 100 people pushing or merely 99.

 

[pkguy57]

The reasons I ask are:
1) I remember reading somewhere that the first person would be able to hold back 100 people pushing against him in this configuration for some reason. But I can't explain to my son why.
2) We were watching "Finding Nemo" and discussing whether the fish all swimming down would really affect the net bringing them up. I said that unless all the force was tranfered to the net, a fish swimming in the middle or the back of the school would not make a difference.