How would you calculate this?

[Diddums x]

For all we know you might be the man that pulls the chain with your toilet cleaning gang!

Nah, I have minions for that

I'll do the crap jobs if necessary but I tend to stick to the H&S and compliance side of things nowadays, as well as organizing projects, materials, PPE, COSHH, all that other lovely exciting stuff (yawn).

 

[Ryan-3]

I just did a fraction of the difference in speeds my head, still arrived at 54MPH.

 

[Avenged7Fold]

MPH

That's no SI unit!

 

[Armageus]

That's exactly how I worked it out too. Thing is, there's this line at the end of the question:

Answer the question, giving your answer to a suitable number of significant figures and explaining your choice of significant figures.

Wut?

Not sure how bounds ties in to the above que though as it is quite specific in the speed and the time taken, they aren't rounded figures.

Oh and in answer to the question I got exactly 24 m/s using the fact that again at GCSE level (you did say it was a GCSE que) students are expected to use 1 mile = 1.6 km or 5 miles = 8 km, so 432,000/18,000 = 24 m/s

I assume that it allows for slightly different answered e.g. if you actually used 1 mile = 1.61 km or 1 mile = 1.60934. E.g. if you used 1.61, then the overall answer would be expected to 2 decimal places.

 

[Gammawolf]

I can't believe how many people are not aware of SI units.

 

[encephalopathy]

if you think about it there would also be the tiny variation when he accelerates from 50mph to 60mph. they haven't however told you the rate of acceleration or the time required for it so i guess they are looking at the SI units aspect of the answer

 

[Rilot]

if you think about it there would also be the tiny variation when he accelerates from 50mph to 60mph. they haven't however told you the rate of acceleration or the time required for it so i guess they are looking at the SI units aspect of the answer

They generally assume a dv/dt of infinity for these sorts of questions. They would be giving times if they expected you to use v=u+at.

 

[=XDC=FluphyBunny]

I can't believe how many people are not aware of SI units.

Given most people don't use or are not even aware of the terminology of SI units, why would it be so surprising?

 

[Deleted member 66701]

You wouldn't think I'm a head engineer for a team of 6 guys in a maintenance company, would you?

No.

 

[glenimp617]

BODMAS

 

[Greebo]

I don't know what SI units are, but I got 54 mph

Firstly work out the distance travelled at each speed
3*50=150
2*60=120

Total travelled is 270 miles

150+120=270

divide the total miles travelled by the total time drove.

270/5=54mph

That's what I got and how I done it, I have no idea what an SI unit is either.

m/s is SI. mph isnt

 

[Glaucus]

Given most people don't use or are not even aware of the terminology of SI units, why would it be so surprising?

even if you don't, just ignoring an important part of the question is pretty silly. the fact it asks for SI and significant figures, would strongly suggest just mph is wrong, without any knowledge of what SI actually is.

 

[Destination]

I assume that it allows for slightly different answered e.g. if you actually used 1 mile = 1.61 km or 1 mile = 1.60934. E.g. if you used 1.61, then the overall answer would be expected to 2 decimal places.

Aye it is likely reasonably to round off, given they stated the speed was 50 and 60mph, not 50.0 and 60.0 but nm.

 

[skaif]

BODMAS

No longer a thing apparently, BIDMAS is all the rage now.

 

[Clarkson]

I like to mix things up with the american version PEMDAS

 

[Destination]

I like to mix things up with the american version PEMDAS

trumpism....

 

[adolf hamster]

Pfft, z-plane is just a diagram for imaginary numbers. Everything is fine as long as you stay inside the unit circle

no! its witchcraft i say!

funny i wrote on the last pages of my notes for that module "and that is why we get computers to do everything for us these days"

 

[platinum87]

54mph is better than m/s because m/s requires too many decimal places.

That question should be changed to kph instead of mph

If i can say 1 mile = 1.6, than i can also just assume pi = 3.0, mavity can just be 9 meters per second per second...

And we can all just commit suicide after all of that.

 

[Avenged7Fold]

54mph is better than m/s because m/s requires too many decimal places.

That question should be changed to kph instead of mph

If i can say 1 mile = 1.6, than i can also just assume pi = 3.0, mavity can just be 9 meters per second per second...

And we can all just commit suicide after all of that.

Your wrong, the question is for SI units and so THAT is better.

Being comfortable with base units is one of the aims, not reduce decimal places. He is studying engineering not rounding numbers in primary school. Physicists don't describe the speed of light as 300 mega meters per second just to make the length of the number sorter. If need be you write it multiplied by 10 to the power of something but still in SI units.

Also your assumptions of decimals should be the same: so if one mile = 1.6, then pi - 3.1 and mavity would be 9.8.

The point of calculating in SI units is to make people comfortable when working out values that are different from what you are given eg. acceleration from time, displacement and velocity values.

 

[jimjamuk]

Part of a degree course is you have to go find out stuff yourself - so the flag in that question was "SI" which meant if they didnt teach it to you direct they expect you to figure this out yourself. It'll get worse, much worse with stuff you need to work out yourself