Analysis of a system of bodies where all forces are in balance and there is no motion relative to a chosen reference frame.
Questions tagged [statics]
645 questions
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Why is the shape of a hanging chain not a "V"?
From Wikipedia:
To answer this question: "What is the shape of a chain suspended at both ends?" we can use the variational principle that the shape must minimize the gravitational potential energy.
The gravitational potential energy is highest at…
Jossie Calderon
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45
votes
7 answers
Hanging a hammer from a table and a stick so that its midpoint is outside of the support of the table
I came across this pic on the internet today. At beginning I thought it is just not possible because the centre of mass is way off so gravity will generate torque making the stick and hammer fall. Later I thought that the heaviest part of hammer…
Tanishq Jaiswal
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32
votes
7 answers
Why won't a tight cable ever be fully straight?
I posted this picture of someone on a zipline on Facebook.
One of my friends saw it and asked this question, so he could try to calculate the speed at which someone on the zipline would be going when they hit the water.
The only answer, which was…
Tango
- 423
30
votes
2 answers
Why are arched bridges stronger than flat bridges?
To keep the question brief: in bridge design, why is the arch structure favoured compared to a simple flat one?
In other words, how does the curved platform alter the force decomposition of the load on the bridge, such that it can uphold larger…
user929304
- 4,910
25
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Why does the curve of a hanging chain not minimize the area below it?
If we have a chain of fixed length hanging from two points we know that it will form a curve that minimizes the chain's potential energy.
If we imagine the chain as having many small segments, then the potential energy of each segment is $E_p =…
jan
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7 answers
Why does the weighing balance restore when tilted and released
I'm talking about a Weighing Balance shown in the figure:
Press & Hold on onside of the horizontal beam and then release it. It makes some oscillations and comes back to equilibrium like shown in the figure.
Both the pans are of equal equal masses.…
claws
- 7,493
22
votes
7 answers
Plank overhanging off a building — where does the normal force go?
Suppose there is a (uniform rectangular) plank of mass $m$ and total length $L$ that is on top of a building with some piece overhanging or jutting out past the building. Assume it isn't past the point where it tips over, so assume it stays in…
MaximusIdeal
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What holds up the lowest point of a rope following a catenary curve?
A catenary curve is the curve followed by a rope suspended at both ends in uniform gravity.
I thought I would try to solve it myself because it seemed like a good challenge, but almost immediately I got stuck on this question.
Given that nothing is…
Devsman
- 1,683
15
votes
6 answers
How does this tensegrity table work?
I have assembled below a desk toy which seems to defy laws of physics at first glance (objects can be placed on top of it up to a certain limit, since it is already under strain).
The toy is in fact an example of a tensegrity sculpture, where a…
Tom
- 1,447
12
votes
6 answers
Is the weight of something being dropped the same as the force of something being static?
If I have a block of let's say: 10 kg and I put it over my foot in a static manner, what we know from static mechanics is that my foot is opposing the weight of the 10 kg mass with the same force in opposite direction to maintain equilibrium, which…
Gabo
- 165
12
votes
5 answers
Why can't a rope be pulled completely straight?
I have found several discussions on how to calculate the sag of rope that is tied off at two points (like a tightrope), and I understand it to a certain extent. What I can't wrap my head around is how come it is impossible to pull the rope tight…
silvermaple
- 225
12
votes
5 answers
Two people are holding either end of a couch, is one person exerting more force than the other?
I was carrying a couch with my flatmate yesterday, and I started thinking about this.
Often when carrying objects like this, one person will be taller and has thus lifted his end of the couch higher than the other person's. Additionally, one can…
dwjohnston
- 397
11
votes
3 answers
Determining forces on a table with four legs and an object placed on a random point
We have an object with weight $D$ at a given location on table wit with four legs ($F_1$ to $F_4$). What is the force applied on each leg? (for simplicity, I'm just using the same labels $F$ and $D$ for both the location and the force)
$W$, $H$,…
Shapul
- 133
11
votes
6 answers
What is the role of pillars in bridges?
As I can see in the picture, there are so many pillars which are holding the bridge. This picture gave a question to me that what are these pillars doing below the bridge?? An appripriate answer could be "these are providing support to bridge".
I…
Vidyanshu Mishra
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Hydrostatic friction: why do water droplets stay at rest on an inclined glass surface?
This is a non-expert question on a (seemingly simple) text-book topic.
The question is about "hydrostatic friction", defined as follows.
Consider a drop of water resting on a flat surface. If the surface is slightly
inclined, then the drop will not…
Slaviks
- 4,493