I completely missed the collisions approach when I first tried to solve this and tried using the work-energy formula. I am wondering if this approach can be made to work? Here is my attempt:
So I let the work done on the ball be ##W_b## and work done on spring be ##W_s##. Then $$W_b=\Delta K =...
Yeah, sorry about that. Since I'm posting one at a time now (to avoid spamming) and taking time to read responses etc I figured it won't take that much extra to rework the problems, so that is what I'll be doing from now on.
The origin of the force is the blades pushing down the air. Of course...
My thinking was that the power produced by a falling object is P=Fv=(-mg)(-gt)=mg^2t. So it depends on t, ie the "counter power" must also depend on t if it is to balance it, right? But author's solution is a constant. I know I am making a mistake somewhere.
Note: Apologies for the lack of...
Right I get it now. I wasn't taking into account that not only the fuel is ejected (I only realized after re-reading BvU's comment - thanks BvU!) Also for some reason I only just realized that the fuel is actually in the plane rather than somehow converted from the air into fuel!
Anyway, as...
Dear jbriggs
I think I understand what you're saying. Does this mean that the escelator doesn't apply the same force throughout but changes it based on how many people there are? But that doesn't sound right to me for some reason. (I am of course not saying that I am correct here!) I think my...
Thanks for the help everyone!
So it seems my problem was seeing a speed and immediately thinking P=Fv was the most appropriate formula. Is there any way of making this work? Probably not but I'm not that good so it's still worth asking!
I honestly am still confused. I think it is a problem I am having with understanding the problem statement. I feel that this is one of those problems where if someone could explain to me the PS in detail I would find the problem trivial!
Right, so I made the mistake of using 45lb instead of 42. When I use 42 I get $$(42lb\cos 27)(12min)(6.2mi/h)\left( \frac{10^{-5}N}{2.248\times 10^{-6}lb}\right)\left(\frac{60s}{1min}\right)\left(\frac{0.3048m/s}{0.6818mi/h}\right)=332210=3.32\times 10^5 J$$
Thanks everyone, I understand where I went wrong now - I was trying to stop an object moving in circular motion by stopping its circular motion, but this doesn't stop the object (by NI)!
I think this is what the author does but I still don't understand it. I think I am just misunderstanding the problem statement but here is my working out:
This is probably where I am going wrong as I don't completely understand the PS but I am visualizing it as follows: some air goes into the...
Sorry about the lack of working and I appreciate everyone's detailed responses. I take down my questions as I read as I have limited internet time. Then I post down when I have written much later on, meaning I don't have time when I post them to actually go through the working for every single...
Dear site Mentors
I made some threads recently in this section which got moved to the homework section.
They are not homework. I am an adult well past university age who has been studying physics for fun so I can understand modern research. I am far from reaching that point yet but I feel that...
Author's solution seems to assume that "carry 100 people/min" means "takes 100 people up the whole length / min", ie 13.3m/min=0.222m/s. But its lengthwise speed is actually 0.620m/s.
In particular, why is my solution wrong (according to author's solution)? :
I said since 100 people/min then...