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Temp

Homework question

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Temp    167

This question caused some debate with my kids tonight.

 

Q: What does a Newton Meter measure?

 

a) Momentum

b) Torque or moment

c) Acceleration

d) Force

 

Vote now...

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Ferdinand    413

Without looking it up, and remembering my O-level classes.

 

Not d) A Newton measures force.

 

Not c). Acceleration is measured in Metres per Second per Second - a very intuitive way of expressing that unit name - change in velocity per second or dV/dT.

 

Unable to remember the unit name for momentum, but momentum is 'reluctance to slow down' and remembering the similarity between being charged into by a large dog slowly vs a small dog more quickly, it suggests the relevant unit dimensions will be Mass x Velocity or Kilogramme Metres per Second, so not a).

 

Which leaves my vote for b). And since Torque is Distance from the pivot x Force Applied, analysing the dimensions says that that is Metres x Newtons or Nm.

 

Ferdinand

(who may have got the details wrong, and put his foot in another Lighthearted Thread)

 

Edited by Ferdinand

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Crofter    251

Well, as written, a Newton Meter is surely an instrument for measuring the number of Newtons, therefore force.

However if @Temp actually meant a Newton Metre then yes, it's torque.

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jack    417

If they mean "newton metre" (should be no capitals when written like this), then it's torque.

 

2 hours ago, SteamyTea said:

Recently a Tesla was put on a dyno and they measured 920 foot-pound when it was in ludicrous mode.

http://jalopnik.com/here-is-how-much-torque-the-tesla-model-s-p100d-makes-o-1792688704

 

Blimmin' flip! O.o

 

Edited to add: the question is worded even worse than I thought. What does it measure? A meter measures. A unit (eg, a newton meter) doesn't "measure", as such.

 

Not sure whether this question is very clever or very stupid!

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Temp    167

Crofter & dpmiller win. I thought it was torque but the answer was d) Force.

 

A Voltage Meter measure Volts so a Newton Meter measures Newtons (eg Force).

 

As for capitals... As I remember units are capitalised if they are named after someone so V for Volts, m for meters, N for Newtons etc.

 

Edited by Temp

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jack    417
Just now, Temp said:

As for capitals... As I remember units are capitalised if they are named after someone so V for Volts, m for meters, N for Newtons etc.

 

The abbreviations are capitalised. When the full word is used, it is not. From https://en.wikipedia.org/wiki/SI_base_unit:

 

"The names and symbols of SI base units are written in lowercase, except the symbols of those named after a person, which are written with an initial capital letter. For example, the metre (US English: meter) has the symbol m, but the kelvin has symbol K, because it is named after Lord Kelvin and the ampere with symbol A is named after André-Marie Ampère."

 

 

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JSHarris    869

It's also worth noting that when an SI unit that is named after an individual is used, and so capitalised, it is convention to use a space between the numerical part and the symbol.  When an SI unit is used that is not named after an individual, but refers to a physical property, then the convention is to have no space between the numerical part and the symbol. So, when we write a velocity of 3.5 metres per second, it should be written 3.5m/s, when we write a voltage of 3.5 volts we should write 3.5 V.  Interestingly, it is common to write units named after people in full without capitalisation, hence volts (after Volta), amps (after Ampère) and watts (after Watt) are all in common usage, even though their abbreviated form should be capitalised.

Edited by JSHarris

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jack    417
22 minutes ago, JSHarris said:

It's also worth noting that when an SI unit that is named after an individual is used, and so capitalised, it is convention to use a space between the numerical part and the symbol.  When an SI unit is used that is not named after an individual, but refers to a physical property, then the convention is to have no space between the numerical part and the symbol. So, when we write a velocity of 3.5 metres per second, it should be written 3.5m/s, when we write a voltage of 3.5 volts we should write 3.5 V. 

 

Bugger, I learned something. Hate it when that happens! :$

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SteamyTea    213
5 hours ago, Temp said:

d) Force.

Not sure that is right.

Bit like saying MPH measures only miles.

Edited by SteamyTea

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JSHarris    869
1 hour ago, SteamyTea said:

Not sure that is right.

Bit like saying MPH measures only miles.

 

 

Should be mph, not MPH....................:D

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