Pendolino speeds from the trackside

[eMeS]

Is this about right?

To estimate the speed of a 9 car Pendolino, time how long it takes passing a fixed object and divide 420 by the time in seconds to get mph.

 

[generalvegitable]

that would give you the time in metres per second, to get the speed in kph you would use this formula. to get mph simply multiply divide the resultant by 1.6

(S*60*60)/1000

(where S is speed in m/s)

 

[RyanB]

That would assume that it was travelling at a constant speed. There are a number of variables that would have to be considered.

 

[jopsuk]

that would give you the time in metres per second, to get the speed in kph you would use this formula. to get mph simply multiply the resultant by 1.6

(S*60*60)/1000

(where S is speed in m/s)

to get to mph, you need to DIVIDE by 1.6. Your value in mph should be smaller than that in km/h, as a mile is longer

 

[Nym]

That would assume that it was travelling at a constant speed. There are a number of variables that would have to be considered.

They don't change speed that quick...

 

[ainsworth74]

That would assume that it was travelling at a constant speed. There are a number of variables that would have to be considered.

I don't think we're going for accuracy to 3 decimal places here so assuming the measuring distance isn't ridiculously long (say a maximum of a kilometer) and you're not measuring at a time when you know the train is either changing speed for a station then you should get a fairly accurate speed.

 

[Eng274]

Assuming all mile posts are 1/4 mile apart, it is possible to time the distance between 2 mile posts and apply it to this formula:

(1/4t)*3600

To get mph, where t = time to cover a quarter mile. Using some form of stopwatch obviously!

That method is pretty inaccurate though, as the human error measuring the time must be pretty significant!

 

[swt_passenger]

Both of the last two posters have failed to notice that in the first post the OP is in a fixed position, and he is measuring the time for the fixed length of the train to pass him.

Using mileposts, or places 1km apart, is not what he was getting at.

 

[generalvegitable]

to get to mph, you need to DIVIDE by 1.6. Your value in mph should be smaller than that in km/h, as a mile is longer

sorry, I keep getting those 2 mixed up, I study A level physics, I should know this, anyways I'll correct it

 

[eMeS]

Both of the last two posters have failed to notice that in the first post the OP is in a fixed position, and he is measuring the time for the fixed length of the train to pass him.

...

Thank you , and my bold emphasis - I was beginning to have serious doubts about what I'd originally posted.

So, 420 divided by time in seconds gives something close to the average speed for a 9 car Pendolino to pass a fixed point?

 

[swt_passenger]

Thank you, and my bold emphasis - I was beginning to have serious doubts about what I'd originally posted.

So, 420 divided by time in seconds gives something close to the average speed for a 9 car Pendolino to pass a fixed point?

I think your constant needs to be much higher, around 485?

I'm taking the train to be 217m (713 ft) long, as 390 carriages are nearer 24m on average.

Therefore as 60 mph is known to be 88 ft per second, so 125 mph is 183 ft per second, and at that speed a 'pass by' would take 3.89 seconds.

Please feel free to find my maths wrong though...

Trouble with this is you need a stopwatch with at least tenths to be useful.

 

[eMeS]

I think your constant needs to be much higher, around 485?

I'm taking the train to be 217m (713 ft) long, as 390 carriages are nearer 24m on average. ....

Not knowing much about Pendolinos apart from them being currently 9 cars in length, I used a figure of 615' from this reference where on closer reading, I've just spotted that the article is discussing 7 car train-sets.

Doh!

 

[scotsman]

I think it's worth pointing that any speed you got would be an average

 

[SS4]

that would give you the time in metres per second, to get the speed in kph you would use this formula. to get mph simply multiply divide the resultant by 1.6

(S*60*60)/1000

(where S is speed in m/s)

1.6? I hope that's a typo for 3.6

I found an easy way to convert from mph to m/s is to multiply by 4/9. To go from m/s to mph multiply by 9/4 - it's reciprocal.


Of course the speed of anything is given by v(t) = d/dt s(t) . Needless to say for your application that would be overkill and average speed would be good enough on a good site.
Are you trying to work out the speed to apply the Doppler Effect per chance?

 

[generalvegitable]

deleted

 

[eMeS]

...
Are you trying to work out the speed to apply the Doppler Effect per chance?

No - it's just that I've filmed several Pendolinos and others taking the Wolverton Curve, and I thought it might be interesting to see what speed they were doing. Some seem to hammer through, whilst others, I guess, are still picking up speed from a stop at Milton Keynes Central.