I put 105 kg on a vertical spring. It stretches down 0.0065 m. Effective spring constant?
In this instant I know there is gravitational force down, Fg = mg.
Taken place is displacement of the spring downward.
Spring force opposes displacement, so it is upward.
Since the stretched spring is held stretched, net force is 0.
So gravitational force equals elastic force.
Thus Fg = Fe.
Fg = mg.
Fe = -kΔx.
Now, my problem is my signs. So up is positive, down is negative.
mg = -kΔx
(105 kg)(-9.81 ms⁻²) = -k(-0.0065 m - 0 m)
-1030.05 kgms⁻² = -k(-0.0065 m)
158,469 = -k
k = -158,469 N/m ?
1) What is the negative sign in F = -kx ? It is really confusing me!
2) And what is "effective" spring constant?