# The Motor Boat

Discussion in 'Physics & Math' started by Motor Daddy, May 31, 2013.

1. ### James RJust this guy, you know?Staff Member

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It's convenient for you not to respond to what I wrote. I see that. You'll make just about any excuse to avoid facing up to your absurdities.

Just to be clear on your position:

Would it be possible, in your opinion, to determine the speed of the current if you only know the boat's speed in calm water and the time taken for the boat to travel a known distance along the embankment (in the current, not in calm water)?

If so, how would you do it?
And can you show us how your method would apply to the question given in the opening post?

Also: would it be possible to calculate in advance how far the boat would move along the embankment in a given time, if you knew the speed of the current and the boat's speed in calm water? If so, how would you do that?

3. ### dumbest man on earthReal Eyes Realize Real LiesValued Senior Member

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TIME! ??
In first post you stated time at 1 hour 30 minutes! That was ROUND TRIP time. Time was FIXED/KNOWN- Distance was FIXED/KNOWN - WOT speed was FIXED/KNOWN -Current Relative to Bank was FIXED/UNKNOWN ! I was under the apparently wrong idea that we were trying to figure the UNKNOWN speed of the current relative to the bank!
As an aside, at least tell me - would it matter if the first leg of the journey was upstream or downstream as long as it was ROUND TRIP in 1 hour 30 minutes?
Still trying to learn!

5. ### Motor Daddy☼☼☼☼☼☼☼☼☼☼☼Valued Senior Member

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James, No absurdities on my part. I make no excuse for truth, I just tell it like it is. Some people don't like truth, because it conflicts with their beliefs. Not my problem.

No.

You mention the speed of the boat in "calm water." If the boat's speedo measures the closing speed between the boat and the water, and the boat's speedo is reading 8km/hr, where do you get that there is "calm water?" Calm compared to what, the boat? Surely not, because the speedo is reading 8km/hr, not 0 km/hr. You're confused again, James. Einstein really did a number on you.

There is an embankment, a boat, and water.

We are going to measure how much time it takes for the boat to travel 8km along the embankment when the water is stationary to the embankment. It takes exactly 1 hour for the boat to travel the 8km along the embankment in one direction from the start point that's marked on embankment to the end point that's marked on the embankment, and then an additional 1 hour to return to the marked starting point on the embankment. The entire 2 hours the water never changed position according to the embankment, so we say that the water is "still water." The boat's speed in one direction was 8km/hr, and the boat's speed in the other direction was 8km/hr.

Now we are gonna perform the test again on the other side of the embankment, where the water is not stationary to the embankment. First we measure the motion of the water compared to the embankment. The water has a closing speed of 3.27km/hr compared to the embankment, and we'll call that "current water."

So we are going to measure how much time it takes for the boat to travel from the same two points on the embankment, but this time the water is "current water."

I am saying you need to measure the time from the start point on the embankment to the end point on the embankment, and then measure the time from the end point on the embankment back to the start point on the embankment.

You are saying, nonsense, no need to measure, because we know the speed of the boat in still water. I then say, nonsense, we need to measure the times in each direction to find out how much time it takes for the boat to reach each marked location on the embankment.

Do you see where your error is now?

No.

7. ### dumbest man on earthReal Eyes Realize Real LiesValued Senior Member

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Motor Daddy, you seem to use the word "no" as an answer quite a bit.
Also not sure how "Closing Speed" would apply to a Still Boat in Calm Water.
Does my ignorance preclude you from answering my questions, as in the old "refusing to have a battle of wits with an unarmed person", or am I just too dumb to see the TRUTH (regardless of my beliefs)?
Forgive me saying this, but after reading this forum over and over - it almost seems that the "TRUTH" is something that you see as "OPTIONAL" in any given situation. Also. how does " Einstein really did a number on you " add in any way to the conversation?
Again, I am sorry - I truly am only on this forum to learn and to engage in the free exchange of ideas and hopefully, knowledge!!
I have met and conversed/exchanged ideas with people many times more intelligent than myself on many occasions. Tell me, Motor Daddy, have you ever?
I have also met people that openly stated that they "are indeed the smartest person they have ever met" and even had one fellow tell that he indeed was "so intelligent that he did not have to think before he spoke".
I realize that there is indeed that level of intelligence out there - I also realize that I can never hope to achieve that level. Is it my inability to conceive of that level of intelligence or ever being able to achieve it - that makes me unworthy of your response?
Maybe I am just having "an Einstein really doing a number on me" !!

8. ### Neddy BateValued Senior Member

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It sounds like Motor Daddy is saying that we cannot know for certain, (without experimental verification), that velocities can be summed. That's strange, because he seems to accept summation of velocities in his own "MD Theory." I think part of the problem is that the water is not a solid, so he is skeptical of velocity summation for this particular problem. I doubt he would object to summation of velocities for the case of, (say), a motorcycle traveling along the top of a train.

Another reason he might be having so much trouble is because he might not be accustomed to word problems, as given in mathematics classes. I was taught that we are supposed to neglect anything that is not explicitly mentioned in a word problem. For example, in the boat problem, there is no mention of wind, so we should neglect it. But Motor Daddy seems to be looking for "100% accuracy" which suggests that he does not understand that we are neglecting any unknown which is not given in the original problem. He is probably thinking about things like wind, turbulence when the water flows over the embankment, etc.

Or maybe it is just that he is so uncomfortable with the idea that velocities are relative. I notice he has taken to calling relative velocities "closing speeds" to avoid using the "R" word. Maybe that's all it is. Maybe rejecting Einstein has done a number on him.

Last edited: Jun 26, 2013

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11. ### eramSciengineerValued Senior Member

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Motor Daddy is the "dumbest man on Sf".

12. ### quantum_waveContemplating the "as yet" unknownValued Senior Member

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Oh Eram, I saw you had posted and was going to say "hi", but then when I see you are flaming and not posting meaningful content, well ... what is your point in posting at all?

13. ### James RJust this guy, you know?Staff Member

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You replied:

I can't see any chance of progress from here on, given this response.

I think you need to go and do some real-world experiments for yourself, as Pete suggested earlier. You need to start to get a feel for what a frame of reference is, and I don't think you're going to get there via any kind of theoretical approach. It has been years now, and you've made no progress that way so far.

Since you think that the problem in the opening post actually has no calculable solution, then it is natural that you will dispute each and every demonstration presented to you that an answer can in fact be calculated. Hence, we have very little that we can discuss. To have a useful discussion, it is necessary to agree on some basics. Since you have no concept of what a frame of reference is, progress is impossible at this point, as far as I can see.

For the sake of completeness, I'll respond to the rest of your post, though.

The boat's speedo reads 8 km/hr whether the water is flowing with respect to the embankment or not. If it makes it easier for you, you can assume that a boat speed of 8 km/hr is the maximum the boat can achieve through the water.

Calm just means flat water that doesn't present any special impediment to the boat's motion.

The boat is travelling relative to the water when its speedo reads 8 km/hr.

Agreed. This is what we mean when we say "the boat travels at 8 km/h in calm water".

You can do that if you like, but there's no need.

There's no need, because a simple calculation will tell you the times it will take in each direction.

It would be a great idea to do the experiment to check the theory, of course, but I can assure you that the theory involved here has been thoroughly tested in practice and has been found to work excellently.

So, while you obviously have no option but to do the experiment, since you can't do the theory, I have no such restriction. I can do the calculation and get the correct answer, all without ever having to go the experiment.

Moreover, I can do something you can't conceive of. I can go backwards from the travel times to deducing the current speed, purely using the power of my mind. In fact, I have demonstrated as much earlier this thread.

No. Where is my error? It seems I can do everything you can do, only much more.

Look:

See? You can't do it, but I can!

14. ### eramSciengineerValued Senior Member

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Well, there's really no point in having this thread in the first place, since Motor Daddy is not making sense at all.

15. ### James RJust this guy, you know?Staff Member

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So, I take it we're done here.

16. ### Motor Daddy☼☼☼☼☼☼☼☼☼☼☼Valued Senior Member

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I'm done. I appreciate your comments, James. As I said long ago, I have the utmost respect for you. If your last name didn't start with the letter "R" then I would have to assume your name to be Bond, James Bond.