Question

A string 20cm long is stretch 25cm by a load of 50n . what will be it's length when stretched by 100n assuming that the elastic limit is not reach

Answer 1

We can use the formula:

stress = force/area
strain = change in length/original length

where stress and strain are proportional up to the elastic limit.

Let's first find the original area of the string:

A = (π/4)*d^2
A = (π/4)*(0.1cm)^2
A = 0.00785 cm^2

Now let's find the original stress:
stress = force/area
stress = 50N/0.00785 cm^2
stress = 6,369.43 N/cm^2

Let's find the strain caused by the 50N load:
strain = change in length/original length
strain = (25cm - 20cm)/20cm
strain = 0.25

Now let's find the new stress caused by the 100N load:
stress = force/area
stress = 100N/0.00785 cm^2
stress = 12,738.86 N/cm^2

Since stress and strain are proportional up to the elastic limit, we can use the original strain to find the new change in length:

strain = change in length/original length
0.25 = change in length/20cm
change in length = 5cm

Now we can find the new length:
length = original length + change in length
length = 20cm + 5cm
length = 25cm

Therefore, the length of the string when stretched by 100N will be 25cm.