26
votes
Why does "potential energy" have the word "potential" in it?
Because it has the potential to produce mechanical work.
- 24.3k
24
votes
Accepted
How do suction cups work?
TL;DR: Its not the air that's enclosed inside that creates the force, but the lack of air - or more precisely pressure.
First of all some nomenclature (this is for the closed type, there is also the ...
- 24.3k
19
votes
Accepted
Why does "potential energy" have the word "potential" in it?
potential (adj.)
Capable of being but not yet in existence; latent or undeveloped.
The block is stationary and therefore not performing work. If the block never moves, the potential energy remains ...
- 7,307
17
votes
Accepted
Would a centrifugal flyweight governor system slow down the descent of an object that is free falling down to the Earth's surface? (Revised design)
Once the cylinder is released and starts to accelerate downward, the rotating flyweights should pivot upwards to a certain degree (as shown in the drawing) and should act as a drag on each of the ...
- 1,943
13
votes
Accepted
Is radians a dimensionless quantity?
radian is a derived unit, defined as the ratio of arc length to radius. As the ratio of two lengths it is dimensionless.
- 939
12
votes
Do outer fillets|chamfers also reduce stress as inner ones do?
Sorry for not taking your "Thin Hollow Brick-Shaped Object" as an example - I felt a standard notched test specimen would illustrate the principle more clearly:
It can be seen that adding external ...
- 7,771
9
votes
What is Saint Venant Principle?
The intuitive meaning of Saint Venant's principle is that "if two different sets of applied loads are statically equivalent, then the differences between the two stress patterns they create are only ...
- 12.6k
8
votes
What is Saint Venant Principle?
To add to @alephzero's answer, here's an layman's explanation of Saint-Venant's Principle: far enough away from the load's point of application, equivalent loads can be treated as identical.
For ...
- 13.1k
6
votes
Accepted
How to Calculate the Minimum Radius a Rod Can Can Be Bent Staying in the Elastic Range?
If we're staying within the realms of beam theory, we can go with this approach which is valid for any material that exhibits linear-elastic behaviour before yield:
The curvature of a beam is related ...
6
votes
Why is the Stress vs strain diagram preferable to the Load vs displacement diagram?
The Load-Displacement (or Load Extension) and stress strain diagrams are two diagrams identical in shape. See below.
The main visible difference is the values on axis (which are at first glance ...
- 24.3k
6
votes
Why does "potential energy" have the word "potential" in it?
In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, attachments, electrical charge, magnetic field, mass, etc., and ...
- 71
5
votes
Glass panel engineering at work
Glass tends to contain quite a lot of residual stresses from the manufacturing process and these will tend to be concentrated near corners (depending on how the sheet was manufactured). There is also ...
- 15.3k
5
votes
Force required to rotate an object on a plane - moment of inertia?
Since the friction is not known, the torque to overcome that friction can't be known either. You therefore can't do what you want since the problem is under-constrained.
- 11.4k
5
votes
Accepted
Failure in torsion
As a rule of thumb:
When brittle materials are subjected to torsion they fail in the plane, where tension is at its highest, i.e. at a 45° angle.
Ductile materials on the other hand fail in the plane ...
- 1,186
5
votes
Accepted
Are the points of inflection and contraflexure the same?
A point of inflection is defined as the point where a function changes from convex to concave or vice versa.
For a function $f(x)$, this is frequently mathematically defined as the point where $f''(x)...
- 13.1k
5
votes
Would a centrifugal flyweight governor system slow down the descent of an object that is free falling down to the Earth's surface? (Revised design)
jpa made a good answer on why the weights wouldn't flex upwards. I'll add another point. Newton's third law says that for every action, there is an equal and opposite reaction. For the box to be ...
- 151
4
votes
How I can compute cutting processes with continuum mechanics?
Real-world engineering example
To my knowledge there are no simple analytical methods of determining whether an object such as a sword can cut cleanly through any arbitrary object. In manufacturing ...
4
votes
Accepted
Finding downward force of lever bar
The input force is 18.5+20.5 ft away from the fulcrum and the load is 18.5 away from the fulcrum.
This means the force applied to the load is $\frac{(18.5+20.5)}{18.5} = 2.1$ times greater than the ...
- 6,281
4
votes
Accepted
polar moment of inertia for compound shape
Without looking up all the formula's for you, the approach to this problem is rather simple. Find the polar moment of a solid cylinder, and subtract off the
polar moment of the holes.
For the off ...
- 939
4
votes
Thin walled pressure vessel
Both Axial stress, (parallel to the axis of cylindrical symmetry) and Hoop Stress (in the tangential direction) are "Normal Stresses".
They are "Normal", because, if you consider an infinitesimal ...
- 7,771
4
votes
Accepted
Cutting tool for hollow tubes
Probably a skilled metalworker will come along and lough at me for this, but I don't think you can cut to 0.1 mm accuracy with many hand tools. I see these ways:
using a small saw (your tubes are ...
- 4,791
4
votes
Eulerian and Lagrangian descriptions of velocity
The motion is
$$
x = \varphi(X, t) \quad \leftrightarrow \quad X = \varphi^{-1}(x, t)
$$
The Lagrangian velocity is
$$
V(X, t) = \dot{\varphi}(X, t) = \frac{\partial \varphi (X, t)}{\partial t}
$$
...
- 1,453
4
votes
Is strain energy the same as potential energy, or something differen?
This has been asked and answered numerous times before: https://www.quora.com/Why-is-strain-energy-equal-to-1-2*force*displacement-What-about-the-remaining-half basically, it's because you're ...
- 7,771
4
votes
Accepted
A way to calculate the magnitude of the moment
This is a trigonometry question.
Point B is a certain distance upwards from Point A. How much? You know the distance that it is to the left from Point A ($2\text{m}$) and the angle that it is from ...
- 7,771
4
votes
Accepted
Moments of Fixed-Fixed Beam
When trying to figure out whether or not a given reaction will exist at a given support, it's worth remembering what a reaction actually is.
A reaction is the means by which the support resists the ...
- 13.1k
4
votes
Accepted
what is the physical interpretation of poles and zeros of a mechanical system?
The poles and zeros of a LTI plant or system in relation to their eigenvalues determine how quickly a system will stabilize or destabilize and if it oscillates.
When looking at these in the complex ...
- 729
4
votes
Accepted
Converting Newton's Second Law Differential Form to Integral Form and Integration Limits
Review of Terms
w(t) -> v(t) -> velocity at time t
z(t) -> x(t) -> position at time t
...
- 156
4
votes
Accepted
Solving for stiffness matrix numerically by a set of measurements
This is feasible and can be used to modify a theoretical stiffness matrix calculated by the Finite Element method to match experimental results more accurately. The FE model can then be used to ...
- 12.6k
4
votes
Accepted
Would this air amplifier attachment increase a leaf blower's effectiveness?
probably not, here is why.
the coanda effect describes how a moving mass of air entrains nearby air and sets it in motion. So if we start with an extremely fast-moving but small jet of air, with it we ...
- 15.3k
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