VeritasVosLiberabit

It's negative because the force is attractive for x>0.

 

 

 

Look at ratios of forces. G will cancel.

ah I see now.

y = kx -> F = G( m*M/r^2)

y = F = N = (kgm)/s^2

x = (m*M)/ r^2 = kg^2/m^2

k = y/x -> G = [(kgm)/s^2]/(kg^2/m^2) = [(kgm)/s^2](m^2/kg^2) = m^3/s^2kg or m^3 kg^-1 s^-2

should have done this mathematically from the beginning instead of trying to use intuition, thanks for pointing this out.

So I have really been pondering this question for the past few weeks to find the relationship between this constant 'G' and its relationship in the equation for the force of gravity between two massive bodies. The equation for a proportionality relationship is y = kx. This formula looks familiar because Hooke's law is nearly identical to this except 'k' is made negative (not sure why but perhaps because spring rest is 0 in cartesian plane and spring force direction opposite of x?). Anyway, 'k' represents a constant and a constant is a variable used to show a relationship between two or more coordinates. In our case with gravity, we want to see how the force of gravity increases or decreases between any two massive bodies. The two factors that have significance in changing our gravitational force are distance and mass. *The strength of the force of gravity changes at a ratio of 6.673 * 10^-11 for every kilogram of mass with respect to the distance in meters (squared). Basically, this gravitational constant tells us by exactly what interval the force of gravity between these two massive bodies changes. F = mg is just like the equation y = kx. Its the equation for proportionality between two coordinates. this formula is simplified because g = GM/r^2. I'm still not very sure how Newton could have derived the formula F = (M1 * m2) / r^2 without the gravitational constant, because to me it still seems you would need a constant of proportionality in order to calculate exactly by what factor the mass and distance change the force of gravity between the two bodies. It seems that without that number you can understand the relationship among mass and distance and the force of gravity but no actual calculations could be obtained without a constant. Perhaps this could be due to my currently low understanding of different units systems. Some final thoughts I had on the force of gravity: I started wondering why we don't use an intrinsic gravity number in which we can say this planet has a mass of 'x' kg therefore it has an intrinsic gravitational pull of 'x' newtons, similarly to voltage in a battery. But then I remembered that a potential difference, which is the potential energy between two points, constitutes the number representing voltage for a battery and the current is more important than the voltage anyway. But I came to the conclusion that maybe we don't have this intrinsic number because mass in itself is already somewhat of an "intrinsic "gravitational number." Mass tells you that if the number is really high there will be lots of gravity. So gravity is a number that will tell you the influence it has on a specific object which is incredibly useful. I hope what I have written was clear enough to understand my interpretations on the variables associated with the formula for gravitational force.

* I put an asterix by this sentence because this phrase here brought up a inquiry for me. How can we set this constant to m^3/(s^2kg) just to get the units to cancel? Why should the units need extra help to get cancelling from what should be a unitless ratio?

I have some questions regarding the gravitational constant and Newton's theory of gravity. To start, I am a first year physics undergrad student just so you have a sense of my caliber of understanding. Here is my question. As I understand Newton was able to come up with an equation for the gravitational force of attraction between any two massive bodies F= (M1*m2)/d^2

Later, Henry Cavendish invented an experiment in order to find the gravitational constant (6.673 * 10^-11 kg^-1*m^3*s^-2), originally intended to find the density of Earth, which happened a number of years after Newton's death. Cavendish's constant was about 1% off the number we use today. What I'm trying to understand is what is the purpose behind the constant or proportionality. Why is the gravitational constant even necessary, especially if Newton was already able to derive the original equation for the force of gravity between any two massive bodies without this constant? What I'm mostly looking for is a better understanding for constants of proportionality. mu_0 (permeability constant in magnetic field equation) is also an example of a constant I'm still having trouble understanding the purpose of. I simply am having trouble understanding why the main variables involved in these processes simply aren't enough to satisfy their respective equations, why is a proportionality constant so necessary?

I had some questions about the atom that hopefully some of you may be able to answer.

First question: How is it that electrons don't attract to protons within the nucleus and just annihilate with each other? They both have 1.6*10^-19 C charge that would attract one another. The only thing I could think of is there is some other type of force repelling the the electrons from the nucleus? This is just a guess at trying to explain this phenomenon.

Second question: Why are electrons confined to specific energy levels? I don't understand how an electron can only be at specific distances from the nucleus.

Third question: Why do neutrons even need to be paired within the nucleus to balance protons? The charge of an electron and the charge of a proton already cancel each other out to form a neutral atom. Why is the neutron even necessary?

Fourth question: I'm having trouble wrapping my head around non-integral spin. What exactly does it mean for a fermion not to have an integer spin? Maybe spin doesn't mean exactly what is traditionally associated with the word spin. Is this the rotation of the particle or does spin denote a special property about the particle, similar to how the term isospin is used simply because its properties are easier to explain in terms related to spin.

Fifth question: I understand there are two types of particles fermions and bosons, but could someone explain some of the intuitive differences in these particles. How can a force carrier be a particle. I think perhaps fermions are more intuitive because they represent the building blocks of what we see everyday constituting hadrons and leptons, but bosons seem a little less intuitive. For instance, how does a gluon transfer color charge? does it pass through quarks carrying the color charge/anticolor charge with it? are photons and W+ W- bosons inside of fermions waiting to be released through particle interactions?

Hopefully these questions don't sound too elementary or absurd, but I am a new physics student simply trying to gain a little more intuitive clarity on some of these concepts. Math is welcome, however I only have a basic understanding of calculus 1. Thanks in advance.

Hello scienceforums community. I'd like to introduce myself to start because I am somewhat of a new member. I am a physics undergrad but I'm very fresh into the realm of physics. I would like to ask some questions I've had about magnetism in order to give some better insight into what it is exactly.

1) Of course when talking about magnetism you have to talk about electricity. The equation B = {(mu)(I)}/ {2(pi)r} is an equation used to compute the magnetic field induced by a current carrying wire. I was curious to know what exactly mu (the permeability constant) represents in the equation and what makes it so important.

2) When calculating the strength of a magnetic field induced by a current we use an equation like the one I mentioned in the first question. What equation do we use in order to compute the magnetic field strength of a permanent magnetic or a magnet without a magnetic field induced by a current?

3) What is the difference between the electrostatic force and the electromagnetic force?

4) With magnetic flux and Lenz's law, what actually is taking place on an atomic level for a current to be produced by a moving magnetic field? Also why does the area change the magnetic flux?

Hopefully these questions aren't too basic, I'm really just interested in finding thorough and intuitive explanations behind some of the answers for a better understanding of these concepts.