Open study

is now brainly

With Brainly you can:

  • Get homework help from millions of students and moderators
  • Learn how to solve problems with step-by-step explanations
  • Share your knowledge and earn points by helping other students
  • Learn anywhere, anytime with the Brainly app!

A community for students.

Why is kx=25N instead of -kx=25N?

See more answers at
At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.

Get this expert

answer on brainly


Get your free account and access expert answers to this and thousands of other questions

shouldn't F=-kx?

Not the answer you are looking for?

Search for more explanations.

Ask your own question

Other answers:

Ahh this my physics teacher went over
cool! Now you can explain it to me :)
the negative explains how that force is acting upon the spring
it depends on the what you're trying to find
if you're trying to find the force the spring is exerting on the mass or the mass exerting on the spring
Hmmm let's see|dw:1353379482698:dw|
well I guess we're stretching to a certain length, so the first figure?
I mean the first figure you drew
the figures are the same
it depends on whether you're trying to find the length of the spring or the position of the mass
Uhm I think we want my figure because In your figure we have to consider the gravitational force and the restoring force. I don't think they want to consider the gravitational force
if it asked abouthe spring itself it'd be negative
there is two ways this question can be answered 1) How long did the spring stretch from initial 2) What is the position of the mass after initial. They're the same thing
so since it's asking for position of the mass it's this|dw:1353379915405:dw|
why is it positive? because it is going in the direction that we designated as positive?
technically this question can have 2 answers + answer and a - answer depending on how you set up your axis
OH I see! |dw:1353380068540:dw| Like so?
Now I can say that F=kx
no the other way around, I should probably make the restoring force positive...
yeah the picture they used was probably a free falling mass
and saying that the sum of the force of gravity + any other force = F
Yeah that makes more sense. so they probably had up as positive and down as negative.
yes but it really just depends on what you define it... if your teacher marks you wrong and your diagram says otherwise just clear it up with him
so why is k(0.2) why 0.2? How did they come up with x=0.2?
never mind
that's the displacement haha
yes the displacement will still be posive
hmm interesting: (this the DE part of my calc II book) \[2\frac{d^2x}{dt^2}+128x=0 \text{ has the solution }x(t)=c_1cos8t+c_2sin8t \] yeah that's easier that doing it manually....
It's convention to designate potential energy as negative. The reaction force of the spring is opposite the positive applied force.
More clearly: The negative sign of F=-kx means that the spring force is opposite to the applied force on the spring.
potential energy as positive...the restorative force?
Yes that makes sense
I had to reread the last sentence you wrote several times, but it makes sense now
but where did they get the 8 in sin and cos 8t
As others mentioned above, it's a sign convention. You define what direction you want to be positive and anything opposite to that is negative. The norm, though is to treat spring force as negative/opposite to any force acting *on* the spring.
The 8 is based on the period of the spring - that is determined by the spring constant, k, and the attached mass.
\(\large T=2\pi \sqrt{\frac{m}{k}}\) T^-1 is the frequency of oscillation.
yep, sounds good. I googled it LOL \[T=2\pi \sqrt{\frac mk}\]
The "8" in the cosine function usually goes by the name, omega, \(\large \omega\). Might want to look that up too.
so the formula is \[x(t)=c_1cosTt+c_2sinTt\]
so T is \[\omega\]
\(\large . . . cos(\omega t) . . \) No, ω is related to T.
Oh \[\omega=\sqrt{\frac km}\]
\[x(t)=c_1cos\omega t+c_2sin\omega t\]
Yes, you can either derive that using the Diff.Eq. or look it up on a physics formula sheet. (Depends on if you are more mathematician or engineer ;-) )
leaning more towards engineering....physics formula sheet :P
omega doesn't seem to have units
That would be my choice too, but know that the way the physicists got those formulas in the first place was to solve the DEs (or rather to get their math dept. grad students and TAs to do the solving for them..)
omega should have units of s^-1, it's a frequency.
Or .. is at least based on a frequency, something in the derivation might make the units cancel, but I'm pretty sure it's just the reciprocal of the time period, T.
radians per second
according to my friend wiki
so s^-1 should be sufficient, i can leave the radians part out in my notation?
Yes, because radians are dimensionless (it's derived from length ÷ length), that's what the 2π conversion factor is in there for.
Oh I see
why is c_2 zero? shouldn't it be when we say\[ x(0)=8c_2 cos8t\] does that mean \[0=8c_2 cos8t=8c_2cos(0)=8c_2(1)=c_2\] yep that seems right LOL
Thanks everyone!!!!

Not the answer you are looking for?

Search for more explanations.

Ask your own question