percieved size?

[razorboy]

I'm not sure if this is actually the right forum to ask this question in, if not please kindly direct me to where I need to be. If something that is actually 255.33 feet long is viewed at a distance of 1800 feet, how long in centimeters would it appear to be?
Thanks,
rb

 

[wjm11]

If something that is actually 255.33 feet long is viewed at a distance of 1800 feet, how long in centimeters would it appear to be?

You need to define your problem a bit more. For example, if you hold a ruler at arm's length and view a distant object just above the ruler's edge, you might say the object is 5 cm long. If you move the ruler closer to your face, the same object might appear only 2 cm long (along the edge of the ruler). Thus, it is necessary to know not only the distance to the object, but also the distance the ruler is held from your eyes. Make sense?

This type of problem falls under the category of "similar triangles."

 

[razorboy]

Yes, I think that does make sense.
Thanks, Dave