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# Why is it as Humans that we have not yet come up with a way to measure speed?

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• 18-07-2023 11:58am
Registered Users Posts: 16,131 ✭✭✭✭
Ms

For instance if a vehicle is doing 100kph that just says that if you stay in that vehicle for an hour you will have covered 100 kilometers. It does not actually tell you the speed the vehicle is travelling at.

If you do 60 kph or 120 kph and it is constant for that hour then it just tells you how much you covered in that hour but not the actual speed that you were going. Its just the force you were applying to cover that distance.

So you have the distance you covered and the time it took you to cover that distance if it was constant but no actuall measurement of the speed it took to do that.

Maybe I am just overthinking all this lol.

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Peace and long life.

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#2
Registered Users Posts: 10,721 ✭✭✭✭

I don't think anyone could ever read that post and accuse you of overthinking

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#3
Registered Users Posts: 3,543 ✭✭✭

Speed = Distance / Time

= m/s

km/hr

m/hr

etc

Do you suggest a new unit of measurement such as speeds?

E.G. - I got to work early travelling at 135 speeds

edit: on reflection you might be onto something - E.G. - knots

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#4
Registered Users Posts: 9,034 ✭✭✭

If you travel 100km in one hour, then your average speed is 100km/h. Of course, there may be parts of the journey where you're travelling slower than that, and parts that you're travelling quicker.

But if you're using a device to measure your speed in real time (speedometer, GPS, etc), it will tell you your current (instantaneous) speed (to within a certain tolerance of accuracy) over the course of the journey. It will show you starting off at 0 and ramping up to 100km/h, then maybe slowing down to 80km/h taking a bend and speeding up to 120km/h coming out of the bend and onto a straight. It's dynamically measuring your speed as you travel.

As pah said, speed is the relationship between distance and time, but that doesn't mean that you have to have travelled 100km in an hour to calculate that you're travelling at 100km/h. You could hop in your car and hit the accelerator and 15 seconds later your speedo would show that you're travelling at 100km/h, even though you've only travelled a few hundred metres. It doesn't mean that you need to gave travelled 100km for it to calculate that.

Its just the force you were applying to cover that distance.

When you're measuring speed, you're not measuring force at all. The force required to move the object to or at a particular speed would depend on the mass of the object, friction, wind resistance, etc. There would be more force required to move a truck to a speed of 100km/h than to move a bicycle to 100km/h (in the same conditions).

If you do 60 kph or 120 kph and it is constant for that hour then it just tells you how much you covered in that hour but not the actual speed that you were going.

This is exactly what speed is. Speed is the rate at which an object covers distance, so you can't measure it without referring to rate (time) and distance. I think you're getting hung up on the difference between average speed (total distance covered divided by the time interval) and instantaneous speed (observed snapshot of measured speed at a distance approaching zero) . But both can be easily measured.

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#5
Registered Users Posts: 16,244 ✭✭✭✭

I think you've done too much speed.

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#6
Registered Users Posts: 16,814 ✭✭✭✭

Nah, he'd have figured it out by now with a few wraps of daycent gear 😉

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#7
Registered Users Posts: 267 ✭✭

If you really want to delve into this topic you should look up the Heisenberg uncertainty principle. Turns out some very smart people have already tried to find the answer only to come up against a fundamental limit of the universe.

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#8
Moderators, Society & Culture Moderators Posts: 39,528 Mod ✭✭✭✭

Of all the strange questions by certain posters. This takes the biscuit. I’m out of this thread at 126km/h (speed measurement).

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#9
Registered Users Posts: 3,403 ✭✭✭

For instance if a vehicle is doing 100kph that just says that if you stay in that vehicle for an hour you will have covered 100 kilometers. It does not actually tell you the speed the vehicle is travelling at.

That is exactly what speed is

Distance = Speed x Time. If Usain Bolt is running at at 12 metres per second for 9 seconds, he has run 108 metres.

Time = Distance / Speed. If Usain Bolt ran 108 metres at a speed of 12 metres per second, he ran for 9 seconds.

Speed = Distance / Time. If he ran 108 metres in 9 seconds, his speed was 12 metres per second.

If you travel 87 Kilometres in 38 minutes and want your speed in Km/H. First convert the 38 minutes into hours by dividing by 60 and then your speed will be 87 / 0.63 = 138 Km per Hour.

You could ask how long does it take a car going 138 Km/H to travel 87 Km. Distance divided by speed. 87/138 = 0.63 of an hour.

What distance will a car travel if it is moving at 138Km per hour for 0.63 of an hour. 138 Km per Hour * 0.63 Hours = 87Km.

If a caterpillar can travel the length of 13 AA Batteries in 42 seconds, how fast is it travelling in AA/Min? We want the speed, we know the distance expressed in AA Batteries, and we know the time in Seconds. Convert the time to minutes (0.7). 13/0.7 = 18.57 AA/Min.

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#10
Registered Users Posts: 10,847 ✭✭✭✭

It’s all relative, generally speaking.

“It is not blood that makes you Irish but a willingness to be part of the Irish nation” - Thomas Davis

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#11
Registered Users Posts: 2,033 ✭✭✭

I feel the need, the need for the bus that couldn't slow down.

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#12
Registered Users Posts: 16,182 ✭✭✭✭

I have a court case for speeding coming up soon. Will you represent me?

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#13
Registered Users Posts: 12,344 ✭✭✭✭

Aircraft have two ways of measuring it,

Airspeed and ground speed.

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#14
Registered Users Posts: 12,344 ✭✭✭✭

Of course the real question is...

"What is the airspeed velocity of an unladen swallow?"

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#15
Registered Users Posts: 12,471 ✭✭✭✭

I have one coming up for possessing speed, same question?

“I can’t pay my staff or mortgage with instagram likes”.

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#16
Registered Users Posts: 14,249 ✭✭✭✭

100 Kph is Mach .0081. Sorted

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#17
Registered Users Posts: 35,048 ✭✭✭✭
Master of the Universe

Tell me you don't know how speed is measured by... telling me you don't know how speed is measured.

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#18
Registered Users Posts: 6,005 ✭✭✭

But we do have a way to measure height. It could be barely, it could be not at all, it could even be as a kite. Speaking of, pitot tube - static port instruments are one of the few ways of measuring speed directly. Indeed, the speedometer on the car and the GPS speed are indirect measures, i.e. they are actually measuring distance and time and then compute speed.

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#19
Moderators, Category Moderators, Arts Moderators, Sports Moderators Posts: 49,705 CMod ✭✭✭✭

but that's all that speed is? distance covered in unit time.

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#20
Registered Users Posts: 1,447 ✭✭✭

African or European?

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#21
Registered Users Posts: 910 ✭✭✭

Wait until I tell you that when you accelerate, you change the rate of speed over time, m/s/s or km/hr/hr!

The OP needs to look up the base units of the SI system. Every unit of measurement, no matter the application, is made up from some combination of metre, second, kilogram, kelvin, candela amp or mole.

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#22
Registered Users Posts: 6,755 ✭✭✭

That’s average speed.

Theres no way of measuring speed at a given point in time, as at any given point in time, nothing is moving at any speed.

We can therefore only measure average speed.

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#23
Registered Users Posts: 6,005 ✭✭✭

as at any given point in time, nothing is moving at any speed.

This is not true. We have practical limitations when measuring speed, so what we actually measure is the average speed for a very short time interval, but that doesn't mean speed or movement are not continuous. So when something is moving at some speed, the distance travelled will be zero for a time interval of zero, but that doesn't mean that there is no instantaneous speed.

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#24
Moderators, Category Moderators, Arts Moderators, Sports Moderators Posts: 49,705 CMod ✭✭✭✭

Is this not just stating that 'if no time has elapsed, nothing can happen'?

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#25
Registered Users Posts: 910 ✭✭✭

Pitot tube measures pressure, from which you can calculate speed. But it is a direct instantaneous measurement as it doesn't need a time difference.

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#26
Moderators, Category Moderators, Arts Moderators, Sports Moderators Posts: 49,705 CMod ✭✭✭✭

anyway, that was not the point i was trying to make. speed is stated/measured as distance divided by time, whether we're talking about an average or not. i think - from what you're saying - you're talking about speed as a fundamental measurement of its own, independent of other measurements (such as distance and time). and (going out on a limb here) that's not possible.

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#27
Registered Users Posts: 6,005 ✭✭✭

Correct, it measures pressure (and pressure difference), but it doesn't need a time reference. Time is also not measured directly, instead we count pulses of a known frequency, generated by a mechanical, electronic or even atomic device. Pretty much any measurement is either by comparison with a known measure (length, mass) or by observing its effects on something else (temperature, pressure, voltage), and then again measure by comparison with a known measure.

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#28
Registered Users Posts: 3,852 ✭✭✭

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#29
Registered Users Posts: 2,255 ✭✭✭

Pitot measures pressure, which can then be used to calculate velocity

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#30
Registered Users Posts: 83,640 ✭✭✭✭

Calculus 101:

which is how the kinematic equations are derived:

For vehicles its even easier in practical application, vehicle sensors measure this (usually on the assumption of no-slip condition of tyres etc), for aircraft they use pitot tubes and other derived fundamental physical maths to calculate speed from differences in air pressure at points on the instrument:

OP might thrive in an engineering program.

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#31