# Faster or Slower?

Discussion in 'Physics & Math' started by Motor Daddy, Apr 25, 2022.

1. ### Motor DaddyValued Senior Member

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Did you even read my opening post? Did you go to time 14:45 in the video and understand what I am talking about?

Do you understand I am talking about the craft and the treadmill (that's plugged into the outlet?)

1. Tell me how you measure the speed of the belt BEFORE you put the craft on it? Where is the power coming from?

2. Tell me how you measure the speed of the craft?

3. Which speed is faster? Which ft/sec is greater?

4. Billvon started the conversation of power, because sometimes he gets power and speed mixed up. The title of this thread is "Faster or Slower?" The title of this thread is NOT "More power or less power?"

Last edited by a moderator: May 3, 2022

3. ### billvonValued Senior Member

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We are talking steady state power generation. That's how sailboats work. That's how the desert vehicle worked. Power generation.
Correct. At that point zero power is being produced.
If it is moving at the same speed as the belt, then it is moving with the belt. In the no-air scenario this is what happens eventually. If the belt is infinitely long it eventually matches its speed as the friction in its wheels causes the two motions to cease relative to each other.

In the air scenario, its propeller starts generating power. This opposes the friction in the wheels and allows the vehicle to remain stationary with respect to the frame. The power generated by the difference in speeds opposes the friction in the wheels.
Again, this is trivial to prove wrong, as the two examples I gave above demonstrate.
Because then there is no difference in speed between belt and wind.

However, if you unplug the treadmill, then move it outside where it is windy, the craft can then move upwind on the belt. This is because there is, once again, a difference between the belt and the air - and that's where the power comes from.

However you like. Relative to the frame, relative to the craft or relative to the wind are three options.
Nope. There is not enough information in your statement to figure out what the speed is. If the machine is turned off, then the speed of the belt relative to the frame is zero.

I have to ask. This is high school stuff. Are you really, honestly this ignorant, or are you playing the fool to try to get attention?

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5. ### SarkusHippomonstrosesquippedalo phobeValued Senior Member

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Okay, let's go back to your OP:
Strictly speaking, you're half correct: if the car and a line start at the middle of the treadmill belt, the car will be going faster if it reaches either end before the line reaches its end. However, that is looking at both the speed of the car on the treadmill, and a line on the belt, relative to a fixed reference point, which is not the context of the video. Your argument would have a car that appears stationary relative to this fixed reference point having a zero speed. However, the car is travelling at X speed relative to the surface it is on. And that is the speed being considered, not the speed relative to a fixed point.

So it's all about context, and what one means when one is talking about the speed of the car, or the speed of the treadmill. If you want to get bogged down in only utilising a single reference point, that's okay, but if others don't go with you then it's going to result in a lot of cross-talk. Using your fixed reference point, though, you would be half correct.

Taking the context into account, the speed of the car (i.e. relative to the surface) is faster than the speed of the belt when the car moves forward (toward the controls).

7. ### Motor DaddyValued Senior Member

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Good, we are making progress.

So you acknowledge that if it is not moving with the belt then it is either moving faster or slower than the belt, right?

If the craft is moving with the belt, what is the relative speed between the belt and the craft, zero?

So you're say that if the craft is moving with the belt the relative speed is zero and the belt speed is zero?

Last edited by a moderator: May 3, 2022
8. ### Motor DaddyValued Senior Member

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The speed of the craft relative to the belt is always THE SAME for the belt and the craft. That speed is a CLOSING SPEED of which it is simply the distance that increases over time between a line on the belt and the craft.

Here is the important part:

That closing speed is 1 speed, it is a relative speed between the belt and the craft. There is no "which is faster or slower", because there is ONLY 1 speed.

The ONLY way to have two different speeds, one for the craft and one for the belt is to compare each of their speeds to the frame.

I repeat, a closing speed is a single speed, so there can't be a faster and slower. A single speed of 2 ft/sec is faster or slower than what?

Last edited by a moderator: May 3, 2022
9. ### Motor DaddyValued Senior Member

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So you admit you can't understand High School Physics? If this is only High School stuff, and you don't understand it, which clearly you don't, then which grade physics DO you understand, 3rd Grade?

10. ### billvonValued Senior Member

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If it is moving with the belt (wheels not turning or sliding) then the speed of the vehicle relative to the belt is zero. That does NOT mean that the belt speed is zero, since the belt speed in your example above was measured relative to the frame - and there are many other ways to measure it. Before you define any speed you have to define your reference frame.
Nice try! I am starting to think you really are that limited, and are just lashing out when your limitations are exposed. I would be happy to have you prove me wrong.

11. ### Motor DaddyValued Senior Member

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So are you saying that the craft is faster of slower than the belt if it is moving with the belt? Can the craft be faster or slower than the belt while it is moving with the belt with a relative speed of zero to the belt??

Just so we are clear on your position.

12. ### Motor DaddyValued Senior Member

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Stick around and answer my questions honestly if you have the balls!

13. ### billvonValued Senior Member

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Nope! Not what I said at all. But good job at trying to introduce a strawman.

14. ### Motor DaddyValued Senior Member

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Can the craft be faster or slower than the belt while it is moving with the belt with a relative speed of zero to the belt??

15. ### billvonValued Senior Member

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To repeat from an earlier post: If it is moving with the belt (wheels not turning or sliding) then the speed of the vehicle relative to the belt is zero.

See if you get it this time.

16. ### SarkusHippomonstrosesquippedalo phobeValued Senior Member

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Your language is imprecise: the speed of the craft relative to the belt is only THE SAME for the belt and the craft if the craft is travelling at zero relative to the belt, as the belt always travels at zero relative to the belt.

If you mean that the speed of the belt relative to the craft is the same as the craft relative to the belt, then yes. But that's not the speeds that are being compared: it is a comparison of the speed of the belt relative to the frame, and the speed of the craft relative to the belt. When the craft is stationary relative to the frame and on a moving belt, the two speeds being compared are the same. When the craft moves relative to the frame then it is either moving faster or slower than the speed of the belt (as measured relative to the frame).

It's surely not that difficult to understand, is it?
Changing reference frames from those in the video and saying that they are wrong, or that those using the reference frames in the video are wrong in their analysis, is not particularly helpful.
But, sure, if you change the reference frames being discussed, you'll come up with different answers than those in the video.
Noone is comparing the closing speeds of each. Noone has even suggested that at any point.
Not true, as explained above. Craft is measured relative to the surface it is on (i.e. the belt), and the belt is measured relative to the frame. Not the same frame but different frames. It does that because the speed of the craft relative to the belt is a proxy for the speed the craft would otherwise achieve relative to a surface in the same frame as being measured for the belt speed.
This is a red-herring.
I repeat: the comparison of speeds in that video is of the belt relative to the frame, and the craft relative to the belt. Anything else by you, in changing one or both of those reference frames, is just confusing the issue. While what you say might be correct for those other reference frames, they are not the ones being considered in the video. So you and the video are not talking about the same things, hence you end up with a different result.

17. ### Motor DaddyValued Senior Member

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So the craft moving with the belt with a zero relative speed to the belt is moving the SAME speed as the belt.

Which direction is the belt moving, to the rear? Obviously!

So what needs to happen in order for the craft to be FASTER than the belt? Does the craft have to travel a greater distance towards the rear in the same amount of time?

18. ### Motor DaddyValued Senior Member

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NO! You either missed the point or you are deliberately misrepresenting the concept in order to further your BS!

_____A-------------------B____________
________________ A---------------------------------------------------------------------------------------B__________________

Do you see the distance between A and B on the top line?
Do you see the distance between A and B on the bottom line?

That change in distance occurred over a duration of time. If the distance between A and B on the top is 2 feet, and the distance between A and B on the bottom is 10 feet, then there was a change in distance of 8 feet.
If that change in distance of 8 feet occurred over a duration of 1 second, then the CLOSING SPEED is 8 ft/sec.

Here is the important point that you missed previously:

That closing speed of 8 ft/sec is ONE SPEED for BOTH A and B!!!! There is no "A is faster than B" or "B is faster than A" because it is only 1 speed, and that is a closing speed between A and B. DUH?

Last edited by a moderator: May 4, 2022
19. ### SarkusHippomonstrosesquippedalo phobeValued Senior Member

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YES! You were imprecise in your statement, implying the same speed for both RELATIVE TO THE BELT, which is factually false. You obviously didn't mean what your words implied, which is why I also offered a response on what you possibly meant.
Closing speed is a red-herring! You can repeat ad infinitum that the closing speed is the same for both (which I agree it necessarily is), but noone else is talking about the closing speed, because that concept is not relevant.
Noone else is calculating the speeds of the craft and belt relative to each other. Noone: not the video, nor anyone else on the thread. Only you have brought it up, and now talking about it as if others are disagreeing with what the concept of it is. It just isn't relevant to what anyone else is talking about.

What is relevant are the frames of reference that they are using, as explained already to you. And noone is using closing speeds (i.e. speeds relative to each other). The frames they use are the craft relative to the surface it is on, and the belt relative to a stationary observer (or the treadmill frame etc).
If you use different frames from other people then you will get different answers, but complaining that you're getting a different answer without appreciating that, as you are doing, is really not helpful.

Here's an idea: try agreeing with them what frames of reference you should all use, and see if they come back with a different result to you.
Then try it with different frames of reference, and see if the answers are the same as your previous ones.

20. ### Motor DaddyValued Senior Member

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Your misunderstanding doesn't constitute an error on my part. You continue to misunderstand the concept. Closing speed is NECESSARILY relevant to the topic, as the math has to add up with closing speed and different frames.

If the distance is 10 ft between A and B after 1 second has elapsed, then A NECESSARILY traveled 2 ft compared to the frame, and B NECESSARILY traveled 10 ft compared to the frame. So compared to the frame A's speed is 2ft/sec, and B's speed compared to the frame is 10 ft/sec.

YOU are the one mixing frames by comparing a closing speed (speed of craft compared to a line on the belt) compared to the speed of the belt compared to the frame. That is MORONIC to compare two different frames of reference to compare speeds in two different frames. MORONIC!

The math is A travels 2ft/sec compared to the frame. B travels 10 ft/sec compared to the frame, and the closing speed is 8 ft/sec. It ALL adds up, mathematically! Save your BS for Einstein, he would agree with you by claiming "length contraction" and "time dilation." (rolls eyes)!

21. ### Motor DaddyValued Senior Member

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What you are claiming is that B is faster than A, because A (the belt) is traveling 2ft/sec compared to the frame of the treadmill, and B (the craft) is traveling 8 ft/sec compared to A.
So you are claiming B is 6 ft/sec faster than A.

That is TOTAL BS!

B is 8 ft/sec faster than A, because A's speed compared to the frame of the treadmill is 2ft/sec, and B's speed compared to the frame of the treadmill is 10 ft/sec.

AND the closing speed is 8ft/sec.

YOU LOSE!

22. ### originHeading towards oblivionValued Senior Member

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He is simply an anti-science troll who is here to annoy. He hasn't changed a wit since he was kicked out before. That's why I put him on ignore.

23. ### SarkusHippomonstrosesquippedalo phobeValued Senior Member

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No, the error on my part was taking you seriously.
Nonsense. It is NOT relevant, and the maths DOES add up: speed of treadmill backward (relative to fixed frame) + movement speed of craft forwards (relative to fixed frame) = effective movement speed of craft on a flat length of static road. If in 1 second the car moves 1ft forward while the belt moves 2 ft back, the effective speed of the craft if it were on a flat road is 3 ft/s. Oh, look at that: it all adds up, mathematically!
Sure, relative to the frame. So what. That's not what is being stated in the video. They are not taking both speeds relative to a fixed frame. Why can you not understand that??
Your inability to comprehend doesn't make the analysis moronic.
Noone is talking about closing speeds! Only you. Noone is talking about measuring the speeds only relative to the frame. Only you. Relative to the frame you are correct. But so what? Since that isn't what the video is analysing, you're simply creating a strawman.
Well done.

Anyhoo, my time of taking you seriously is unfortunately at an end.

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