Motor Daddy:
Obviously, others have already tried to walk you through this simple problem since I was last here. But I'll add my comments, just for good measure, in the expectation that nothing will sink in with you, as usual.
So I measure the embankment to have a 1,000 m/s velocity in space using light, but that's irrelevant to you, because it never needs to be known.
Right.
If I send a light signal from one end of the pool where and when the little boat starts traveling, how much time does it take the light to reach the other end of the pool?
That depends on who is doing the measuring. It's completely off topic for this thread, though. We don't need to consider special relativity here - just plain old Galilean/Newtonian relativity, which ought to work even in the Motor Daddy universe - if only you could get your brain around your own theory as well as everybody else here can.
I measure the embankment to have a 1,000 m/s velocity and the river is flowing compared to the embankment. I measure the water's motion using light and the water is at a zero velocity in space. Now what?
Then you work in the embankment frame, same as you do if the embankment has zero velocity, and you get the same answer as before. The embankment velocity with respect to "space" is completely irrelevant to the stated problem. The stated problem only asks for the speed of the current relative to the embankment.
Where does RoS and length contraction and time dilation come into play with the little boat?
It doesn't. We don't need Einstein's theory here, since the speeds are so low. We can even use Motor Daddy physics and things will work out just fine. In fact, that's all I did in posting my original solution above. Did you see anything about length contraction or time dilation there? No, because it wasn't needed. Those effects are there, of course, but in this problem they are utterly insignificant. Besides, you're nowhere near equipped to deal with the relativistic corrections in this problem, when you can't even get to first base and solve the thing using your own Galilean theory variant.
If I had a man climbing a set of stairs on the cruise ship in the x and z directions while the cruise ship was traveling at speed in the water, would the length be contracted the same in the z direction as it is in the x direction?
The length of what?
You seem to be wanting to go off on irrelevant tangents to avoid looking at the actual problem of this thread. Why?
Just solve the problem in the opening post. Then we can worry about all this extraneous rubbish you want to introduce. You need to walk before you can run.
So we mark off 8km on the embankment. How much time does it take for the boat to travel to that mark upstream, 1 hr? We then test again going downstream. How much time to get back to the original point on the embankment, 1 hr?
When there's a current, the boat goes slower upstream than downstream. Do you agree?
Can you then see that it can't possibly take the same time in both directions?
Is this really so hard for you? I mean, all it takes is basic common sense and everyday experience. We're not doing rocket science here.
So you're saying it's the simple and natural thing to do to pretend the water is not moving (no current) when measuring the boat's speed in the water, just like you pretend the ground isn't moving when you measure your walking speed.
If you're using a marine speedometer to measure the boat speed in the water, then it can ONLY measure the speed relative to the water. How could it possibly know what a distant embankment is doing, let alone "space"? It's just a little propeller that is pushed around by the water going past (or something of that sort).
It's just like how it's "natural" for your car's speedometer to "pretend" that the road is not moving. How can the car's speedo know anything about the road's motion through "space"? It can't.
I'm sure you believe what your speedo tells you when you're trying to avoid getting a speeding fine, Motor Daddy. But how can you possibly trust it? You don't know how fast your car is going relative to "space", so your speedo is useless. Right?
Why is it that you have a problem with someone wanting to measure the boat's speed according to the embankment, which we know is at rest like the water is pretended to be when we measure the boat's speed in the water??
I have no problem with that. That's what the problem is about. You need to know the boat's speed according to the embankment to solve the problem. Like I showed earlier. And like everybody else has explained to you. 8 + 3.27 = 11.27. Remember?
You say the Boat speed relative to the water. The water is assumed to move at 3.27km/hr relative to the embankment.
There was no assumption about the 3.27. That was what we calculated from the given information.
How do you know the Boat speed relative to the water when you only know the water speed compared to the embankment?
You've lost track of the problem now. Go back to post #1 of this thread and read the problem.
The boat's speed relative to water - whether that water is flowing at 3.27 km/hr or at 1 billion km/hr or zero km/hr - is measured to be 8 km/hr. The problem then asks us to calculate the water's speed relative to the embankment.
You can't figure out the boat speed compared to the embankment by knowing the water speed compared to the embankment.
Right!
That's why we needed the information about the boat's speed relative to the water as well.
How do you know the boat speed relative to the water when you only know the water speed compared to the embankment?
The boat's marine speedometer tells us! It is 8 km/hr.
Just look at it! A wonder of modern engineering.
Neddy Bate, there is no 8km/hr in the test of the boat in current.
Yes there is. I just saw it on the speedometer reading as the boat was travelling up the river.
What NOT to do when you want to measure the time it takes the boat to travel in CURRENT WATER is to place a boat in still water and find the speed, and then measure the water and find the speed, and then do math and proclaim you have the right answer. That would be downright stupid!
Why? 8 + 3.27 = 11.27, doesn't it?
So as the current increases to a billion km/hr, the boat travels at a speed of eight minus a billion upstream??
Relative to the embankment, yes.
What else would you expect?[/quote]
