5
votes
Can you directly feel the effect of gravity, or only opposing forces?
You are almost completely right.
What we do not and cannot feel is a uniform gravitational force. By “uniform” here I mean in the sense of general relativity where the force of gravity is just a ...
- 109k
4
votes
Accepted
In special relativity, can a transfer of energy increase only the mass of a point particle and not its speed?
Here is a possibly useful energy-momentum diagram (from my answer to How is the time-component of the spacetime interval in a spacetime diagram related to the time component of the energy-momentum 4 ...
- 12.4k
3
votes
Is there a principle that determines the tension in this system?
Apologies for posting a second answer. My first answer addressed what I considered to be the more realistic case of non-infinitely rigid connections. This answer specifically addresses the ...
- 10.1k
1
vote
Is there a principle that determines the tension in this system?
The way to approach friction problems is to consider all the sliding contacts as sticking first and finding the friction force required to enforce the sticking.
Assume all bodies have zero ...
- 3,345
1
vote
Is the $\Sigma$ in Newton's second law the sum operator or an "arbitrary" notation?
This is not a physics question, it's a notation question. In most books, you'll find
$$\sum \vec{F} =m\vec{a}, $$
where $\sum$ is the summation symbol. The expression
$$\Sigma \vec{F}=m\vec{a} $$
...
- 3,440
1
vote
Is the $\Sigma$ in Newton's second law the sum operator or an "arbitrary" notation?
Newton’s law, correctly stated with a summation, is
$$\sum_{i=0}^{n-1}F_i=ma$$
for mass $m$, acceleration of the system $a$, and all $n$ forces considered $F_0,F_1,…,F_{n-1}$.
I don’t know why someone ...
- 3,347
1
vote
In special relativity, can a transfer of energy increase only the mass of a point particle and not its speed?
If it's really an idealized point particle, its invariant mass doesn't change when a force is applied to it. This is a direct consequence of how we define the four momentum of a point particle in ...
- 3,248
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