Force applied causes
deformation in the object. It changes the relative positions of
constituent particles in the crystal lattice.
As soon as that happens, the interatomic or intermolecular forces come
into play and they, tend to restore the solid back to it's original
shape.
This restoring force per unit area is called Stress . When external forces are removed, the internal forces tend to restore the solid back.
This property is called Elasticity .
However, no material is perfectly elastic and what happens is that, the body is not able to restore itself completely.
Answer:
Since the distance between the pivot and its weight is zero, the moment of its weight about the pivot (= weight × 0) is zero. Hence, the weight of the ruler can be ignored.
Hope this helps:)
B. truthfully it's the only one that makes sense
To reduce friction between two surfaces, you have to
make the surfaces smoother.
The best way to do that is to introduce a fluid between them,
like grease, oil, or air.
