Given some parameters, how do you determine how much of an image sensor an object will consume?
The basic idea is that the ratio of the distance/focal length will be the same as the physical/image ratio.

So, assuming a focal length of 100mm, this gives:

$mag=10m/100mm=100$
$size_{image}=1m/mag=10mm$

Note, the distance is the distance measured from the focal point, which will be 1 focal length from the sensor, so that might factor into the equation as well.

See this calculator to play around with things a bit more.