I'll show how you can do this in GIMP, it should be similar in photoshop.

We start with our object on paper. Curves dialog basically shows us histogram of the image. When I click into the image, I can see where in the histogram given area is. This way I can find out where approximately my future white point is going to be.

Then I modify the curve in way that makes tones even a bit darker than our projected point go completely white. The curve basically sets brigtness tone mapping in our image. Original curve projected every tone to the same one, so did not change anything. The curve we have now makes everything above 55% brightness completely white, the second point in the middle tries to keep tones that were originally dark relatively unchanged.

As you can see this curve didn't work completely. I could have pushed the brightness a bit further (e.g. the curve a bit left, to eat out more of middle tones), but I think that would destroy original image too much. If I needed to go through with this I'd probably create another layer in which I'd push it all the way to eliminate the shadow, and than mask it in a way that would only show up in shadow area where I need it, without affecting a low of the object.

Or, our can simply take this as a a starting point and use white brush to kill the rest of the background.