Student sliding bag along floor in elevator

Click For Summary
The discussion revolves around the physics of a student sliding a bag in an elevator, specifically addressing the acceleration involved. The key point is the confusion about why the equation for displacement does not include the term -0.5a_xt^2, as the negative acceleration is already accounted for. The acceleration is expressed as a_x = -α_k (g + a), which is negative, but there is a suggestion that it can be made positive with a different approach. The conversation highlights the nuances of interpreting acceleration in this context. Overall, the participants are exploring the implications of the equations in relation to motion in an elevator.
member 731016
Homework Statement
Pls see below
Relevant Equations
Pls see below
For this problem,
1676877869180.png

The solution is,
1676877943337.png

However, is the reason why they don't do ##-0.5a_xt^2## because the negative of the acceleration has already taken care of itself?

Many thanks!
 
Physics news on Phys.org
The answer seems to make
a_x=-\alpha_k (g+a)<0
negative. You can make it positve one with your setting of ##-0.5a_xt^2##.
 
Reply
  • Like
Likes member 731016
anuttarasammyak said:
The answer seems to make
a_x=-\alpha_k (g+a)<0
negative. You can make it positve one with your setting of ##-0.5a_xt^2##.
Than you for your reply @anuttarasammyak !
 
Reply
  • Like
Likes anuttarasammyak
Thread 'Chain falling out of a horizontal tube onto a table'

Thread 'Chain falling out of a horizontal tube onto a table'

My attempt: Initial total M.E = PE of hanging part + PE of part of chain in the tube. I've considered the table as to be at zero of PE. PE of hanging part = ##\frac{1}{2} \frac{m}{l}gh^{2}##. PE of part in the tube = ##\frac{m}{l}(l - h)gh##. Final ME = ##\frac{1}{2}\frac{m}{l}gh^{2}## + ##\frac{1}{2}\frac{m}{l}hv^{2}##. Since Initial ME = Final ME. Therefore, ##\frac{1}{2}\frac{m}{l}hv^{2}## = ##\frac{m}{l}(l-h)gh##. Solving this gives: ## v = \sqrt{2g(l-h)}##. But the answer in the book...
View full post »

Similar threads

Work done in elevator problem — is it positive or negative?
Replies
3
Views
2K
Newton's laws — Two stacked blocks sliding on a frictionless floor
Replies
17
Views
3K
Questioning the Solution for Elevator vs Rock Problem
Replies
7
Views
2K
Elevator Motion and Bathroom Scale Readings
Replies
2
Views
2K
Solving John's Elevator Problem: Acceleration & Time/Distance
Replies
11
Views
2K
Understanding Sign Conventions in Elevator Tension Problems
Replies
6
Views
3K
Tension in a deformed cylindrical bag on a surface
Replies
18
Views
2K
Understanding Forces and Acceleration on a Sliding Object on an Incline
Replies
3
Views
2K
A Please Explain Elementary Physics Elevator Question
Replies
22
Views
371
Having a hard time learning Newton's 2nd law
Replies
5
Views
2K