Mass And Spring

[ElectricMile]

A 7.00 kg mass hanging from a spring scale is slowly lowered onto a vertical spring, as shown in the figure.

I got the first part, What does the spring scale read just before the mass touches the lower spring? wich was, 68.6 N

Dont understand how to approch, The scale reads 20.0 N when the lower spring has been compressed by 1.50cm . What is the value of the spring constant for the lower spring?....i know im trying to find k

and also, At what compression length will the scale read zero?

wouldnt this be when the mass is all the way on the spring?

[ElectricMile]

anyone got any help?

[Pyrrhus]

Do the forces analysis and Remember Hooke's Law F = kx or in Vectorial form \vec{F} = k \vec{x}

[ElectricMile]

still wondering, i know F=kx, F, being 68.6 and x = 1.5 cm, right? but that k isnt the right answer. i must be doing it wrong, but what?

[Pyrrhus]

You know springs has a restorative force that will restore the spring back to its equilibrium position.

[Doc Al]

It doesn't seem that you've made use of the given information: that the scale reads 20 N. If the scale reading is 20 N, what must be the force the spring is exerting on the mass?

[ElectricMile]

ALRIGHT, heres what i did, mupltipled, 68.6*48.6=3333.4 put that in for my homework online and it says i have a rounding error, i tried 5 diffrent things and it says the same thing, now i have 2 trys or i get a 0, anyone know whats wrong?

[Doc Al]

I have no idea what you are up to with that calculation! Looks like you randomly multiplied two numbers. :mad:

But... if the scale reads 20 N, that means the spring must be providing 68.6-20 = 48.6 N of force. The amount of compression associated with that spring force is given as 1.5 cm. Use F = kx to find k. (Careful of units!)