When a load of $10 \,kg$ is suspended on a metallic wire,its length increases by $2 \,mm$. The force constant of the wire is ........ $N/m$.

Why do spring balances show wrong readings of weight after they have been used for a long time?

Below are two statements. One is labeled as Assertion $(A)$ and the other as Reason $(R).$
Assertion $(A):$ The property of an object that allows it to regain its original shape after the external force applied to it is removed is called elasticity.
Reason $(R):$ The restoring force depends on the intermolecular and interatomic forces in a solid.
In the context of the above statements,choose the most appropriate answer from the options given below:

The material which practically does not show elastic after effect is

What is a perfectly elastic body and a perfectly plastic body?

$A$ wire of length $l$ and cross-sectional area $A$ is stretched by a weight $Mg$ such that its length becomes double. What is the stress in the wire?