A] plot a graph of extension against load using the given data b] find the extension when the load is 2.5n
c] mark the elastic limit (E) or the above spring
d] from the graph write down how extension and load are connected

See the explanation

Explanation:

Load is plotted at x-axis, Extension is plotted at y-axis

(The graph is attached below)

As we can see that within the elastic limit

for x = 1 , y = 5

for x =2 , y = 10

for x = 3, y = 15

We can deduce the function as

y = 5x

So for x = 2.5N

y = 5(2.5)

y = 12.5 mm

(This can also be found by using graph)

Elastic limit is the point beyond which the deformation doesn't follow the function and acts abnormally.

We can see in the graph that after x = 5 N , the graph doesn't follow the function y = 5x , so the elastic limit is at Load 5 N

Extension and load are linearly connected by the function y = 5x where y is the deformation and x is the load. This functions holds up till elastic limit, after which it acts abnormally.

a and b sometimes have a positive value

a.   mass number from atomic number