Question on Newton second's law

  • Thread starter Thread starter UNknown 2010
  • Start date Start date
  • Tags Tags
    Law Newton
Click For Summary

Homework Help Overview

The discussion revolves around a problem related to Newton's second law, specifically involving forces acting on a boy and a seat, as illustrated in a provided image. Participants are exploring the dynamics of the situation, including the forces at play and their directions.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the total mass and forces involved, with one member attempting calculations based on Newton's second law. Others question the completeness of the force analysis and suggest considering additional forces that may not have been accounted for.

Discussion Status

The conversation includes attempts to clarify the problem and identify missing forces. Some participants provide guidance on analyzing the free body diagram (FBD) and emphasize the importance of directionality in force representation. There is an acknowledgment of different interpretations of the forces involved.

Contextual Notes

One participant mentions language barriers affecting their understanding of the problem. Additionally, there is a reference to a sticky topic that may provide context or guidelines for approaching such problems.

UNknown 2010
Messages
77
Reaction score
0
Hello,

This is my first post on the forum, I hope that I will get an answer for my question as soon as possible. :rolleyes:


http://img512.imageshack.us/img512/5765/55503111px2eq6.png

Thanks in advance
 
Last edited by a moderator:
Physics news on Phys.org
Well, what have you done so far? :smile:
 
Hello,

Did you understand my question ?
because it is translated and my english is not good enough .

My try:
Total Mass = 48 kg ==> 480 Newtons

(1)
F=ma
480-250=48a
a = 4.79 m/s^2

(2)
F = 32(10-4.79) = 166 Newtons

I know it is wrong but after I read the sticky topic I saw that I should put my tryhelp me please
 
There is another force acting on the boy+seat which you are not accounting for. Look at the picture carefully to see what that might be.

Also, be careful about direction (upward or downward) and +/- signs. I suggest using + for the upward direction, and - for downward direction.
 
I couldn't find the third foce :cry:
 
In addition to the downward force of weight (gravity):

One end of the rope is attached to the scale, pulling upward.

The other end of the rope is attached to the boy+board.
 
http://img261.imageshack.us/img261/7338/23325527qn0.png
If it is not correct please give me the solution steps
 
Last edited by a moderator:
In your FBD for the board: You have the force "b" acting upward, but the boy exerts a downward force on the board.

In your FBD for the boy: Again, the direction of force "b" is backward. The board pushes up on the boy. Also, you neglected the force on the boy due to the rope he's holding.
 
Thank PF members especially Doc Al

I solved it and I checked the answer from the final answer that is provided under the question and it is correct
 

Similar threads

Replies
9
Views
3K
Replies
44
Views
4K
Replies
4
Views
1K
  • · Replies 14 ·
Replies
14
Views
2K
Replies
3
Views
2K
  • · Replies 7 ·
Replies
7
Views
891
  • · Replies 4 ·
Replies
4
Views
2K
Replies
2
Views
1K
Replies
37
Views
4K
  • · Replies 17 ·
Replies
17
Views
1K