When do I use F=ks instead of F=-ks for Hooke's law?

[david98999]

I am new here and I hope I posted this in the right place.

I understand that Hooke's Law is F=-ks
which states that the spring force is directly proportional but opposite to the difference of the distance from the stretched length of the string and the equilibrium length of the string.

I just have this confusion with my textbook in which there are Hooke's law problems which have been solved using f=ks where the sign of k is not negative and the force sign is also positive.

My question is : with what problems relating to hooke's law would I use F=ks instead of F= -ks?

I hope that I have followed the correct rules with posting this query.

I would appreciate any respone . Thank you.

 

[david98999]

my textbook is physics for scientists and engineers Pearson Randall D Knight 3rd edition

 

[mfb]

I don't have that textbook, but you can get the sign wrong if you define force and distance in opposite directions. Something you should not do because it leads to confusion.

 

[Doc Al]

My question is : with what problems relating to hooke's law would I use F=ks instead of F= -ks?

The purpose of the minus sign is to tell you the direction of the spring force. Use it to figure out the direction, but don't blindly apply the minus sign.

 

[david98999]

thank you for your help doc al and mfb .I really appreciate it