Tensors are used in some engineering calculations. I think the relationship between scalars, vectors and tensors is something like:

Scalar: x

This box weighs x ounces.

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Vector: x, y

I want this box x feet from that wall, y feet above the floor.

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Tensor:

a b
c d

I want to know how much stress (tension-tensor, get it?) the hole for the box places on the wall. I don't remember how to calculate this, just that tensors were useful [Linked Image]

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Here is a proper description of tensors:
http://www.physlink.com/Education/AskExperts/ae168.cfm

You can even apply tensors to Ohms law:
http://www.tf.uni-kiel.de/matwis/amat/semi_en/kap_2/basics/b2_1_3.html