Why Does the Upper Block Fall When Force is Applied Below?

Click For Summary

Discussion Overview

The discussion revolves around the mechanics of two blocks stacked on top of each other, specifically examining why the upper block falls when a force is applied to the lower block, assuming no friction between them. The conversation explores concepts from Newton's Laws of Motion and their implications in this scenario.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question why the upper block does not move with the lower block when a force is applied, given the assumption of no friction.
  • One participant suggests that understanding Newton's Laws could clarify the situation.
  • Another participant emphasizes the relevance of the First Law of Motion, particularly in the context of the absence of friction.
  • There is a discussion about the implications of no forces acting on the upper block, leading to the conclusion that it remains unaccelerated while the lower block moves.
  • Some participants express uncertainty or lack of understanding regarding the application of these laws to the problem.

Areas of Agreement / Disagreement

Participants generally agree on the application of Newton's Laws to the scenario, but there remains some uncertainty about the implications of these laws, particularly regarding the motion of the upper block. The discussion does not reach a consensus on all aspects of the problem.

Contextual Notes

There are limitations in the discussion, particularly regarding the assumptions made about friction and the forces acting on the blocks. The relevance of the First Law is debated without fully resolving how it applies to the scenario.

Who May Find This Useful

This discussion may be useful for students or individuals interested in understanding basic mechanics, particularly the application of Newton's Laws in scenarios involving multiple objects and forces.

Shardul Khare
Messages
23
Reaction score
0
When a keep two blocks one over another...And apply a foce on the block which is below...Why does the upper block falls down..Why dosent it move with A? assumin there's no friction between A and B?
 
Physics news on Phys.org
Shardul Khare said:
When a keep two blocks one over another...And apply a foce on the block which is below...Why does the upper block falls down..Why dosent it move with A? assumin there's no friction between A and B?
Why do you think? Which of Newton's Laws might apply to this situation?
 
phinds said:
Why do you think? Which of Newton's Laws might apply to this situation?
No idea
 
Well, look at it this way. You are surprised that the upper block falls down when the lower block moves out from under it. Ask yourself why SHOULD the upper block move with the lower block?
 
Shardul Khare said:
No idea

Aren't you being a bit lazy here?

Try this. How about you write down, in this thread, all 3 of Newton's Laws? You may copy that from your text, but better yet, state them in your own words to see if you actually not just read them, but comprehend what they say. Then we can jump off from there.

Zz.
 
First Law states that A body continues to be in motion or at rest until an unbalanced force is acted on it
Second law-sEOCND LAW - f=MA
Third Law: Every action has an equal and opposite reaction
 
Shardul Khare said:
First Law states that A body continues to be in motion or at rest until an unbalanced force is acted on it
Second law-sEOCND LAW - f=MA
Third Law: Every action has an equal and opposite reaction

Now, look at your question, and then look at the First Law. In particular, if there's no friction between A and B, how would the First Law be relevant here?

Zz.
 
The Normal and Mg cancel out,no friction means no other force acting on B,right?
 
ZapperZ said:
Now, look at your question, and then look at the First Law. In particular, if there's no friction between A and B, how would the First Law be relevant here?

Zz.
 
  • #10
Shardul Khare said:
The Normal and Mg cancel out,no friction means no other force acting on B,right?
RIght. And what happens to a body with no force acting on it?
 
  • #11
It remains unaccelerated, So when we apply force on the lower bloack,the upper block will stay where it is and the lower block will mover forward, am i right?
 
  • #12
Shardul Khare said:
It remains unaccelerated, So when we apply force on the lower bloack,the upper block will stay where it is and the lower block will mover forward, am i right?
yes, that's where I was leading you in post #4
 
  • #13
phinds said:
yes, that's where I was leading you in post #4
Thank you :)
 

Similar threads

High School Why Does Hooke's Law Use a Negative Sign in Scalar Form?
  • · Replies 30 ·
2
Replies
30
Views
3K
High School Why doesn't static friction move the other object?
  • · Replies 9 ·
Replies
9
Views
2K
High School Are frictional forces action forces or reaction forces?
  • · Replies 14 ·
Replies
14
Views
2K
High School What is the Absolute Value of the Normal force on a block on this wedge?
  • · Replies 3 ·
Replies
3
Views
2K
High School Newton's third law (equal and opposite force)
  • · Replies 40 ·
2
Replies
40
Views
4K
High School What forces are required to tumble a block?
  • · Replies 16 ·
Replies
16
Views
2K
High School How's it possible to push on systems with 2 parts? (Newton's third law)
  • · Replies 14 ·
Replies
14
Views
1K
Undergrad Kinetic friction direction on two stacked blocks
  • · Replies 5 ·
Replies
5
Views
5K
Undergrad Stuck in understanding Newton's 3 laws
  • · Replies 18 ·
Replies
18
Views
3K
High School Newton's 3rd Law interactions with 2nd and 1st Law Partners
  • · Replies 8 ·
Replies
8
Views
2K