Quiz - Physics - Displacement

[scubadada]

Or...187 lbs/64 lbs/cu ft = 2.9 cu ft

 

[Angelo Farina]

kp. It's a nice unit, albeit not quite PC. Allow for some slack, and an answer in kg is quite OK, because a mass of 1kg has a weight of 1 kp. And the kp unit makes for easy mental math. Me, I dont much care if the answer is in kg or kp. The student has a good grasp of the relevant math. If the unit is wrong, that's secondary.

1 kp = 9.81N, BTW

kp ???
Never heard of it. What's the name? What is a "p"??
I do not think that is a SI unit, so we are not allowed to use it in university courses here in Europe...
We must use kg for mass and newtons (N) for force...
It is mandated by law, and a student could report a professor not employing SI units...
Of course we can use multiples or sub-multiples of the standard SI units. So we can use grams instead of kilograms. But the multiples must be by a factor of 10, a factor of 9.81 is not allowed.

 

[Angelo Farina]

If the unit is wrong, that's secondary.

Sorry, on this I disagree entirely. The number can be slightly wrong, but the unit must always be the correct one. Actually, ANY calculation is ALWAYS wrong, as any calculation is always affected by some error.
We can consider the numerical result acceptable if it estimates the "true" value with an error which is judged small enough (but it cannot be zero).
Instead the unit is binary. True or False. If the unit is wrong, it proofs that the student has no physical understanding. I often see heat expressed in degrees, or power expressed in kWh.
When this happens, my student is inevitably rejected and has to repeat the exam...

 

[saxman242]

kp ???
Never heard of it. What's the name? What is a "p"??
I do not think that is a SI unit, so we are not allowed to use it in university courses here in Europe...
We must use kg for mass and newtons (N) for force...
It is mandated by law, and a student could report a professor not employing SI units...
Of course we can use multiples or sub-multiples of the standard SI units. So we can use grams instead of kilograms. But the multiples must be by a factor of 10, a factor of 9.81 is not allowed.

kp is a kilopond. It's essentially the same as a kgf. Common use unit prior to the SI adaptation of the newton in the 1960s and still gets used in certain circles today.

Not to be confused with a kip.

 

[HKGuns]

Easy there professor, these are supposed to be fun.

 

[Storker]

kp ???
Never heard of it. What's the name? What is a "p"??

kp = kiloponds. p = ponds. I'm more than a little amazed that someone whose profile lists them as a scientist hasn't heard about it. It's even on Wikipedia, ferchrissakes. Kilogram-force - Wikipedia

1 kilopond (kp) is the weight of 1 kg of mass at standard conditions. 1 kp = 9.81 (-ish) N.

 

[saxman242]

We must use kg for mass and newtons (N) for force...
It is mandated by law, and a student could report a professor not employing SI units...

This sounds like a law that is doing a serious disservice to the students. In the days of a global economy, having an awareness of multiple unit systems makes one a more capable scientist/engineer. That's not to say that non-SI units are superior, but an awareness that the world beyond the borders of Europe exists.

 

[Joneill]

I tend to disagree

agreed - it's just simple, lower grade-school math - amazed anyone got it wrong... and that is it still being discussed/debated?

 

[Joneill]

kp = kiloponds. p = ponds. I'm more than a little amazed that someone whose profile lists them as a scientist hasn't heard about it. It's even on Wikipedia, ferchrissakes. Kilogram-force - Wikipedia

1 kilopond (kp) is the weight of 1 kg of mass at standard conditions. 1 kp = 9.81 (-ish) N.

Not commenting on what you posted but, as an engineer, I always chuckle a bit when I see someone cite Wikipedia to support a position...

 

[Storker]

This sounds like a law that is doing a serious disservice to the students. In the days of a global economy, having an awareness of multiple unit systems makes one a more capable scientist/engineer. That's not to say that non-SI units are superior, but an awareness that the world beyond the borders of Europe exists.

Well, lbs, BTU and all that crap is a serious PITA and has no merit. Being aware of them and being able to convert to proper units is of course a big advantage, but who in their right mind would want to do calculations in that system?

Just look at the PADI curriculum physics in metric and non-metric units. Sure, they simplify a lot, but still.