Question

the length of a string is 16cm.Its length becomes 20cm when supporting a weight of 5N.Calculate the length of the string when supporting a weight of 6N.Comment on the answer​

Answer 1

Answer:

$20.8cm$

Explanation:

According to hooks law "provide the elastic limit of an elastic material is not exceeded the extension e is directly proportional to the applied force F"

$F= ke$

where F= applied force

           k= spring constant

           e= extension

Given data

length of string l = 16cm

extension  e = 20-16= 4cm

applied force = 5N

we need t o first calculate the spring constant k

apply the formula

$F= ke$

$5=k*4\\k= \frac{5}{4} \\k= 1.25N/cm$

we can now calculate the extension of the string when supporting a 6N weight

$F= ke\\6=1.25*e\\e= \frac{6}{1.25} \\e= 4.8cm$

The length of the string when supporting a 6N weight is

$= length+ extension\\= 16+4.8\\= 20.8cm$

COMMENT :According to the analysis an extra  weight of 1N will cause add 0.8cm to the length of the string