8
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Accepted
Motion of fragments
In general, you would need very precise, and often unattainable, information about the internal structure of the fragmented body, the exact nature of the stresses that caused it to fracture, and a ...
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3
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Motion of fragments
is it even possible to accurately predict the motion of the fragments of an ideal body given that it splits into equal masses?
No, at least, not if all we are given is that the system conserves ...
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3
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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 ...
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2
votes
Trouble with the concept of external force on a system
There are many ways to show that there is another external force acting on the two mass and string system other than the two gravitational forces on the masses and the normal force on mass $m_1$, the ...
- 99.9k
2
votes
Accepted
Is there a principle that determines the tension in this system?
For convenience I will label the blocks as $m_1, m_2, m_3$ from right to left to be consistent with the labeling of the tensions in you diagrams.
For simplicity consider a single block of mass $m$ ...
- 10.1k
1
vote
Accepted
Pivoting rod analyzed about a rotating axis
Two mistakes were made. First, the translational work done by the pin was neglected. By performing similar calculations as was done for the rotational work by the pin, the translation work is found to ...
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1
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Motion of fragments
If we assume that all the fragments have the energy, then for three fragments, we have that the momentum vectors have equal lengths, and their sum is zero. The sum of vectors is geometrically ...
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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
$$\Sigma \vec{F}=m\vec{a} $$
...
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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
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What is the relation between bicycle rear wheel path and front wheel path?
The equation is an approximation to the wheel path - it ignores factors such as rake and the natural tilt that a bicycle takes when turning.
A reasonable model of a bicycle path is to consider the ...
- 3,321
1
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What is the relation between bicycle rear wheel path and front wheel path?
$\frac{R'(t)}{|R'(t)|}$ is a unit direction vector in the direction the rear wheel is moving.
Your formula basically says that the front wheel is exactly distance $L$ in front of the rear wheel, and &...
- 29.5k
1
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Motion of fragments
In a nutshell, is it even possible to accurately predict the motion of
the fragments of an ideal body given that it splits into equal masses?
Why wouldn't it?
For conservation of momentum, if the ...
- 77.9k
1
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How does the steering wheel return to the centre after turning (and letting go)? What forces are causing the self centreing torque?
The simplest instance of using caster angle to give a wheel a tendency to return to a particular orientation is with the type of caster wheel that a shopping cart has, but with the pivot axis at a (...
- 22.5k
1
vote
Accepted
Inconsistent result when finding the minimum speed to reach the highest point of a circular road
The minimum of $v_A$ makes $v_B=0$
The problem is that a car can't reach B and have zero velocity. If it has some tangential velocity, then it can't get rid of it at B since the only forces on it ...
- 42.3k
1
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What is the maximum displacement at which a series of blocks can be displaced vertically?
I remember such a problem, the displacement of cubes placed one on another was only in one direction. The total displacement could be arbitrarily large, and maximum displacements formed the harmonic ...
- 27.5k
1
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How to understand the work-energy theorem?
In this answer I will derive the work-energy theorem twice: Section 1 presents a derivation that straightaway adresses the case of an arbitrary acceleration profile. This approach requires integration....
- 22.5k
1
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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
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Is there a principle that determines the tension in this system?
The problem is poorly worded. "Pulled on a rough surface" could be interpreted to mean the blocks are in motion, in which case the coefficients would be for kinetic friction. But that would ...
- 77.9k
1
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Is there a principle that determines the tension in this system?
You are essentially asking about the distribution of static friction when an extended body at rest on a rough surface is pulled from one end. The answer is that it is indeterminate without more ...
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