Conservation of energy and momentum.
The kinetic energy that the fly has is extremely small - mass of .000001 kg, it's doing 5mph (2.24m/s) northbound, and therefore has a KE of say 0.000025 Joules.
The KE of the train is a bit higher... Say around 100tons mass, then the KE is 101250000 Joules.
The train has to overcome the KE of the fly, and reverse it's velocity vector, and accelerate it up to 100mph southbound. The energy loss to the train is imperceptible... Under standard Newtonian laws, the train CANNOT have an impulse delivered to it to bring its velocity to zero for an instant. Not unless an equal or even large impulse is delivered, and boy will that smart...
You are really not used to being wrong are you, i am going to leave it now ,as you are not really thinking here.
If a car doing 100mph going north hits a wasp doing 5mph going south, does the car stop at impact? And if it does is it too cheap?
pub nonsense, mmmm.... i suspect we are picking over details here. There is a simple principle here which seems obvious to me, and clearly not to you. It is obvious to even pub nonsense that train does not actually stop. it is also clearly true that the actual nub of this question relates to times and distances that are so small to be ignored in any sensible engineering consideration, but it is also true that the two objects share a moment when their velocity is zero, regardless of how short a moment that is, and i do not agree that because it is very short it does not happen. you seem to want to dismiss this event, because it is easier to deal with.
If a car doing 100mph going north hits a wasp doing 5mph going south, does the car stop at impact? And if it does is it too cheap?
You can't trust wasps.
'Grease' is the word, isn't it?
You can't. The little black and yellow bastards.
Wow, I didn't expect that! Has the filter been switched off?
Based on all recorded global airtime data there are two songs that appear in the top 10 most played tunes almost every year. The two songs are connected by one word. Both songs were were in the UK top 5. The word isn't in the titles of the songs.
What is the word ? what are the songs and artist or group that sang them ? What does the word mean ?
No idea but it has got me head scratching
It's a very well known problem, and the genuine answer from minds far greater than my feeble effort, is that the train doesn't stop, not even for the smallest instant. It doesn't share a moment with the fly where its velocity is zero.
The problem is posed to attempt to confuse people by referring to Zeno's paradox and similar ancient world thoughts, stemming from a time before calculus was understood. Now, if you don't or won't understand it, that's fair enough. But please stop telling me I'm ignoring a problem to suggest it doesn't happen, because it's easier to deal with!
Let me turn it round - can you prove that the two bodies have a velocity of zero? Not just state it, but prove it? It's merely a question of physics, so should be straightforward to work out.