If contact forces are repulsive then how are we able to pull stuff? [closed]

Question

I searched a lot on internet(especially physics stackexchange) about the nature of contact forces. I came to know through most of them that it is repulsive in nature which surely means that your hand is not gonna merge within the table as soon as you are gonna make a contact with it.

But I was having trouble with the strings that when a string is tied at the top of a block then at that point of time what is actually pulling the block to keep it stable. How do we explain it at the molecular level(because contact forces are just repelling so what's keeping the block up)?

Edit

We say that it is Tension in the string which is pulling the block upwards but what is actually happening at the molecular level at the lower and upper ends of the string provided that due to Pauli Exclusion Principle (I read this in another answer) the atoms of the lower end of the string and atoms at the top of the block are repelling(how are they then kept together)?

Here is the link of the question where I read that contact forces are repulsive.

Answer 1

It helps to understand what constitutes a chemical bond (without going into great quantum physics detail).

I'll take the example of the hydrogen $\sigma$ bond (aka 'the mother of all chemical bonds') which causes dihydrogen ($\text{H}_2$) to form:

The two $+$ signs represent the hydrogen nuclei (protons), the green ellipse the boundary of the molecule $\text{H}_2$.

Two electrons reside in a so-called $\sigma$ molecular orbital (which doesn't really have a well-defined boundary, here represented by the green line). The ensemble is of course electrically neutral.

The molecule is stable because there's enough negative electrical charge (in the form of the electrons) to compensate for the electrostatic repulsion between the protons.

Following the Morse potential, if we force the two nuclei closer together, electrostatic repulsion increases and so does the molecule's potential energy.

But the Morse potential also increases when we increase the protonic distance. And to break the molecule we have to increase that distance until the so-called dissociation energy is reached.

Of course we can't make a string, rope or bar from hydrogen because it's a gas.

But molecular (as well as ionic) bonds like the $\sigma$ bond (as well as slightly different types like the $\pi$ bond) occur in all types of molecules that make up solid materials. It's the stretching of these bonds and their subsequent increased potential energy that makes the bulk material resist deformation (and resist breaking, up to a point of course).

How do we explain it at the molecular level(because contact forces are just repelling so what's keeping the block up)?

As shown, the inter-nuclear forces aren't always repellant.