Question about inertial and non inertial frames

Click For Summary

Discussion Overview

The discussion revolves around the concepts of inertial and non-inertial frames of reference, specifically focusing on a scenario involving a person standing in an accelerating bus and the implications of friction on their motion. Participants explore the effects of acceleration and the forces involved, questioning the validity of Newton's first law in this context.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • Some participants argue that if person A is on skates with zero friction, they will not accelerate with the bus, questioning where the force would come from to cause such acceleration.
  • Others assert that person A is not accelerating with respect to person B, as the bus's acceleration does not transfer to A without friction.
  • A participant highlights that if A feels no force while the bus accelerates, it seems to contradict Newton's first law in an inertial frame, indicating a misunderstanding in their reasoning.
  • Some participants clarify that without friction, A cannot accelerate with the bus, and they emphasize the necessity of a force to maintain A's motion relative to the bus.
  • One participant suggests a thought experiment involving a ball on a sheet of paper to illustrate the effects of acceleration and friction, prompting further reflection on the scenario.
  • Another participant reflects on personal experience with acceleration in a bus, noting the physical sensation of leaning forward to maintain balance.

Areas of Agreement / Disagreement

Participants express differing views on the role of friction and the implications of acceleration in the scenario. There is no consensus on the correct interpretation of the situation, and the discussion remains unresolved regarding the application of Newton's laws.

Contextual Notes

Participants acknowledge assumptions about the conditions of the scenario, such as the presence of friction and the reference frames involved. These assumptions are critical to the discussion but remain unexamined in detail.

parshyaa
Messages
307
Reaction score
19
Suppose a person A is standing in a bus and bus is accelerating forward then when a person B standing outside observes A he see that A is accelerating in forward direction then there must be a force acting on him which is making him accelarating(because Newtons first law holds in Earth's frame) and he asks him hey A are you feeling a force
Then what will A reply to B?
Assume that he is standing on skates so that friction force is 0.
 
Physics news on Phys.org
If the friction is zero he is not going to accelerate. Where would the force come from?
 
Orodruin said:
If the friction is zero he is not going to accelerate. Where would the force come from?
This is the point
As bus is accelarting so as person A is accelarting with respect to B but person A is not feeling any force then Newtons first law is getting fail in inertial frame
I know something is wrong in my statement, so please point it to me
 
parshyaa said:
Assume that he is standing on skates so that friction force is 0.
parshyaa said:
As bus is accelarting so as person A is accelarting with respect to B
How you have described it A is not accelerating wrt B. The bus is accelerating, but A is just rolling to the back of the bus. The bus’ acceleration is not magically transferred to A: no friction, no acceleration
 
  • Like
Likes   Reactions: Kumar8434 and parshyaa
Dale said:
How you have described it A is not accelerating wrt B. The bus is accelerating, but A is just rolling to the back of the bus. The bus’ acceleration is not magically transferred to A: no friction, no acceleration
Sorry i didn't understand the point
This is the point
As bus is accelarting so as person A is accelarting with respect to B but person A is not feeling any force then Newtons first law is getting fail in inertial frame
I know something is wrong in my statement, so please point it to me
I think something is wrong here
 
parshyaa said:
Sorry i didn't understand the point
If there is no friction, then there is no force to accelerate A along with the bus. It is just that. A will not accelerate with the bus unless there is a force of friction.
 
  • Like
Likes   Reactions: parshyaa
parshyaa said:
Sorry i didn't understand the point
You have assumed that

1. The bus is accelerating.
2. Person A in the bus is accelerating with the bus.
3. Person A feels no force causing the acceleration.

At least one of those assumptions is wrong. Whenever I am on a bus that is accelerating, I feel a force and have to lean forward to maintain balance.

If person A is in the aisle, standing on skates, someone had better open the back door. Because he is going to slide out.
 
  • Like
Likes   Reactions: parshyaa and sophiecentaur
Orodruin said:
If there is no friction, then there is no force to accelerate A along with the bus. It is just that. A will not accelerate with the bus unless there is a force of friction.
Ohh sorry man
This answered my question
Actully i haven't studied the concept of friction so i was having some misconceptions with friction, sorry for this point less question
 
  • Like
Likes   Reactions: sophiecentaur
parshyaa said:
How Foolish question was this
Not foolish - just a process of getting some understanding. :smile:
 
  • Like
Likes   Reactions: parshyaa
  • #10
Try a little experiment. Lay a sheet of paper on a table top, and put a ball on the paper. Quickly pull (accelerate) the paper horizontally. What happens to the ball? Does it move along with the paper, or does it keep the same position, rolling while the paper passes underneath it?

The result may not perfectly match either description, but which one comes closer?
 
  • #11
Have you ridden a bus? What happens if you aren't holding on anything and the bus moves forward?
 
  • #12
parshyaa said:
Suppose a person A is standing in a bus and bus is accelerating forward then when a person B standing outside observes A he see that A is accelerating in forward direction then there must be a force acting on him which is making him accelarating(because Newtons first law holds in Earth's frame) and he asks him hey A are you feeling a force
Then what will A reply to B?
Assume that he is standing on skates so that friction force is 0.

If there was no friction between A's foot and the bus, A would not have accelerated with respect to B. But from A's point of view, B is accelerating backward.
 
  • #13
Dipti said:
If there was no friction between A's foot and the bus, A would not have accelerated with respect to B. But from A's point of view, B is accelerating backward.
Yes, discussion is already over

:welcome:
 
  • Like
Likes   Reactions: Chestermiller

Similar threads

Undergrad Question related to inertia and non inertial frame
  • · Replies 24 ·
Replies
24
Views
3K
Undergrad Forces in inertial and non-inertial frame of reference
  • · Replies 5 ·
Replies
5
Views
2K
High School Inertial vs non inertial frames
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Galilean transformation of non-inertial frame
  • · Replies 35 ·
2
Replies
35
Views
5K
Undergrad Law of inertia (inertial observer and inertial frames of reference)
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad What is an inertial frame? A conflict of two definitions
  • · Replies 83 ·
3
Replies
83
Views
6K
Undergrad Is calling fictitious forces "not real" just about terminology?
  • · Replies 114 ·
4
Replies
114
Views
7K
Undergrad Using reference frames for derivation of Lagrangian
  • · Replies 25 ·
Replies
25
Views
3K
Undergrad Are Newton's Laws just definitions?
  • · Replies 11 ·
Replies
11
Views
2K
Undergrad How earth is a non-inertial frame
  • · Replies 18 ·
Replies
18
Views
6K