Timeline for Why is harder to accelerate object at higher speeds if speed is relative term?
Current License: CC BY-SA 4.0
29 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 27, 2023 at 19:16 | history | edited | Qmechanic♦ |
edited tags
|
|
| Jan 27, 2023 at 19:12 | history | edited | 22flower | CC BY-SA 4.0 |
edited tags
|
| Jan 27, 2023 at 19:05 | history | edited | 22flower |
edited tags
|
|
| Nov 8, 2021 at 10:46 | comment | added | m4r35n357 | This question has been discussed here from several perspectives, even motor mechanics! I just think the SR one is what the poster is looking for ("if speed is relative"). Of course, it is relative in Newtonian physics too but this is not always stated up front. | |
| Nov 8, 2021 at 10:42 | comment | added | PM 2Ring | @m4r35n357 Ok. I was alluding to the issue discussed in physics.stackexchange.com/q/428952/123208 & physics.stackexchange.com/q/44884/123208 etc | |
| Nov 8, 2021 at 10:31 | comment | added | m4r35n357 | @PM2Ring To answer your specific point, equal delta-v makes it easier to compare the effort needed for two acceleration phases! | |
| Nov 8, 2021 at 10:17 | comment | added | m4r35n357 | It should be obvious from the discussion. Amongst other things, this question has an SR tag! And the Newtonian KE is just as frame dependent as the SR "equivalent". Are you really saying it that delta-v is harder to achieve at "high velocity" (whatever that means!)? Because that is what the title is asking about. | |
| Nov 8, 2021 at 1:12 | answer | added | jensen paull | timeline score: 0 | |
| Nov 7, 2021 at 20:52 | comment | added | PM 2Ring | @m4r35n357 Why is equal delta-v relevant? (Newtonian) Kinetic energy is $\frac12mv^2$ | |
| Nov 7, 2021 at 20:18 | answer | added | robphy | timeline score: 3 | |
| Nov 6, 2021 at 13:25 | comment | added | m4r35n357 | Nah, they are answering a different question to the one you are asking IMO. I think you know the answer, so no big deal ;) If a particular observer does not see your two accelerations as equal, it is their problem, not yours! | |
| Nov 5, 2021 at 22:05 | comment | added | 22flower | @m4r35n357 I dont know where my question belong,but my question is clear. Even your answer is most logical to me it seems we are wrong because everbody else are against our logic | |
| Nov 5, 2021 at 21:58 | comment | added | m4r35n357 | I'm commenting on this under the SR tag, if it is now about Newtonian mechanics, I'm out ;) | |
| Nov 5, 2021 at 21:36 | comment | added | 22flower | @m4r35n357 they dont agree with you.physicsforums.com/threads/… | |
| Nov 5, 2021 at 18:03 | comment | added | 22flower | @m4r35n357 Torque at wheels is what accelerate car,we can calculate thrust from torque at wheel.When car increase speed he use higher gears which reduce final torque at wheels,so thrust decrease with speed.From this perspsctive car will accelerate longer from 100-200km/h then from 0-100.. What do you think about this point of view? | |
| Nov 5, 2021 at 15:51 | comment | added | m4r35n357 | I would say: the two accelerations take the same amount of fuel, but the stationary observers will complain (because of their funny money) that the two accelerations were not the same. So you would have to accelerate more the second time to shut them up. | |
| Nov 5, 2021 at 15:32 | comment | added | Bob D | @JurgenM I thought you were only talking about air resistance. In any case, obviously if there was absolutely no resistance the car would burn no fuel to maintain its speed | |
| Nov 5, 2021 at 15:09 | comment | added | 22flower | @BobD I noted without resistance forces,all this forces you mention belong to resistance forces.. | |
| Nov 5, 2021 at 14:59 | comment | added | Bob D | @m4r35n357 Even without air friction, the car burns more fuel as it still has to overcome the kinetic friction energy dissipated in the engine parts, which increases with rpm, as well as tire rolling resistance which also increases with rpm. | |
| Nov 5, 2021 at 14:24 | comment | added | 22flower | @m4r35n357 So car with constant power will have same acceleration and will burn same amount of fuel from 0-100km/h and 100-200km/h,if resistance forces dont exist? | |
| Nov 5, 2021 at 14:19 | comment | added | m4r35n357 | The answers that contradict what I am saying are all using a global frame; energy is frame-dependent (think "funny money") in Newtonian physics as much as it is in SR. Only proper acceleration is physical. I interpret "harder to accelerate" as a "proper" or "self" description, which is how I read the OP. So, you have to choose which you mean ;) Your comments about throwing (accelerating) a ball in a car are correct. | |
| Nov 5, 2021 at 14:12 | comment | added | 22flower | @m4r35n357 I agree with your logic, but at same time understand that car engine with constant power lose "thrust" as speed increase, thrust=power/velocity,so that still leaves me in doubt. so who is right you or members who write answers in my topic? | |
| Nov 5, 2021 at 13:16 | comment | added | m4r35n357 | Who says it does? the delta-v is the same in both cases. There is no difference between 0-100 and 100-200, can you see why? | |
| Nov 5, 2021 at 12:39 | comment | added | 22flower | @m4r35n357 I agree with you but why than car burn more fuel from 100-200km/h then from 0-100km/h, even if resistance forces (aero drag..etc)dont exist? physics.stackexchange.com/q/675339 | |
| Nov 5, 2021 at 12:36 | comment | added | m4r35n357 | It isn't any harder from the object's perspective, and that is where you are going to be physically applying the acceleration. It only appears "harder" from the "rest frame" from which you initially started accelerating but that is not physically relevant to you. | |
| Nov 5, 2021 at 11:17 | answer | added | Professor Sushing | timeline score: 3 | |
| Nov 5, 2021 at 10:18 | history | edited | 22flower | CC BY-SA 4.0 |
deleted 2 characters in body
|
| Nov 5, 2021 at 10:08 | history | edited | Gert | CC BY-SA 4.0 |
added 8 characters in body
|
| Nov 5, 2021 at 9:45 | history | asked | 22flower | CC BY-SA 4.0 |