The statics tag has no wiki summary.
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1answer
210 views
Bridge Trusses?
Which kind of truss would produce the best result (aka. best distribution of force):
i) An equilateral, isosceles or a scalene triangle
ii) 3 small triangles or 2 big triangles (the overall masses of ...
1
vote
1answer
301 views
Problem in a truss [closed]
For the truss above known are the following: l= 1 + 0.02*n [m], h = 2 + 0.01*n [m], F_1 = 200 + 2*n [N], F_2= 500 + 6*n [N], F3 = 400 + 5*n [N], Young's modulus E = 2*10^11 [N/m2], allowable stress ...
3
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3answers
770 views
Deadlifting the rear end of a car with a lever. What it equates to in actual weight?
Consider this youtube video of a guy lifting a car. (skip to 2:15).
I checked, and these cars (PT Cruiser) weigh $1417\:\rm{kg}$. What would the equation be to estimate how much weight he is actually ...
0
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1answer
366 views
Can anyone solve this simple static equilibrium problem? [closed]
A bridge is 50m long, has a mass of 20,000kg, and rests on two pivots, A and B. The distance between A and the left side of the bridge is 10m. The distance between B and the right side of the bridge ...
2
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0answers
555 views
Forces and torques about the CENTER OF MASS of a physical pendulum
I'm currently stumped by the following situation. Say we've got a rectangular physical pendulum (think ruler with a hole-punch at one end).
It's trivial to analyze the motion of the pendulum with the ...
-1
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1answer
123 views
Find largest angle
The two homogeneous bars AB and BC are connected with a pin at B and
placed between rough vertical walls. If the coefficient of static friction between
each bar and the wall is 0.4, determine the ...
1
vote
2answers
95 views
Amount of material required for a pressure tank
I read the answer for the question Why is a hot air balloon “stiff”? and thought something sounded ridiculous. My engineering requirement is that the walls be strong enough. Here $T$ will be the ...
1
vote
1answer
136 views
Finding the contact force in a mechanical problem [closed]
what is the proper FBD for this system. I cant decide since the weight is given, but there is tension and contact forces. Things get mixed up.
Determine the contact force between the smooth 200-lb ...
1
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1answer
168 views
Wave equation from hooke law - simple question
In the paragraph http://en.wikipedia.org/wiki/Wave_equation#From_Hooke.27s_law
it is said, regarding the u(x) function, that
Here u(x) measures the distance from the equilibrium of the mass
...
2
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3answers
548 views
Statics software for structural engineering
I'm attempting to expand my knowledge of engineering software. I've found comsol and ansys for acoustics and thermodynamics/fluid dynamics (not necessarily in that order), now I'd like to see if I can ...
0
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2answers
814 views
Calculation of the maximum load to the bar
Looking for a way of calculating the maximum weight (W) to the rod with the given length (L) where the rod did not break and that only bend for (b) mm.
Need only approximative solution (read: ...
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2answers
1k views
How do I find the tension in additional strings in this problem?
A mass of 5.00 kg hangs attached to three strings as shown in the figure (see image below). Find the tension in each string. Hint: Consider the equilibrium of the point where the strings join.
...
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1answer
463 views
Solving an indeterminate triangle truss structure (statics)
From the setup of two trusses as shown in this illustration, how can I solve for the axial reaction forces in the trusses, and in the points A and B (Ax, Ay, Bx, By)? It is assumed that the joints ...
2
votes
2answers
304 views
Intuitive explanation of moments as they relate to center of mass
I would appreciate it if someone could give me an intuitive explanation of moments. I understand that that the center of mass could be thought of as the point which an object would balance on a ...
4
votes
1answer
536 views
Hooke's Law question
I have the following question to answer:
a force of160 N stretches a spring 0.050m from its equilibrium position.
A. what is the spring constant of the spring?
The equation for Hooke's Law in my ...
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0answers
664 views
Calculating weight using moments [A-Level] [closed]
A uniform plank of weight 150N and of length 4.0m rests horizontally on two bricks. One
of the bricks is at the end of the beam. The other brick is 1.0m from the other end of
the plank.
a) Sketch the ...
1
vote
2answers
295 views
How do you choose the locations of forces when calculating moments?
A uniform bridge of weight 1200kN and of length 17m rests on supports at each end which are 1m wide. A stationary lorry of weight 60kN has it’s centre of mass 3.0m from the centre of the bridge.
...
5
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1answer
215 views
Is this static mechanical balance possible without trickery?
On damnlol.com, I came across this picture:
http://www.damnlol.com/hello-god-i-have-a-fault-to-report-7549.html
My question is: Is this possible without glue? If not are there similar situations ...
6
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2answers
629 views
Hydrostatic friction: why do water droplets stay at rest on an inclined glass surface?
Tjis 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 ...
2
votes
1answer
265 views
Curvature of a cable supporting a suspension bridge in the regime where the mass of the cable is non-negligible
Assume I have a chain of uniform mass, $M_c$, suspended between two points such that it will follow the trajectory of a catenary curve when only supporting its own weight. Let's also say that this ...
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2answers
596 views
Calculate the weight a simple plank can support
I'd like to build a simple desk; just a single plank of wood (or a few side-by-side) with solid supports on each end of the desk. What I'm trying to figure out is how thick a plank I want to use for ...
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1answer
1k views
Moment calculation [closed]
Consider image below. The weight of the fire-fighter is 840 N. What is the torque of the fire-fighter's weight about P and what is the value of the force C which cancels out the torque?
3
votes
2answers
700 views
Formula for implementing a simulated weighing scale
Background:
I'm on the pledge drive committee for a non-profit group, and there is an issue that is always contentious within this group; thankfully the group is amicable, although competitive, about ...
7
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2answers
2k views
What is the force on the arms in a pushup?
What force do the arms have to generate to do a pushup? Let us look a this simplified model:
The body can be represented by the green plank of mass B. Its angle to the ground is $\theta$.
This ...
2
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2answers
1k views
Distribution of forces
(little background: I'm trying to develop a small, quick 'n dirty static physics engine to determine whether a stacking of boxes is stable).
If I have a 3D rigid box (with the bottom in the ...
4
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3answers
607 views
Hanging chain in a planet's gravitational field
The curve for a chain hanging between two poles in a uniform gravitational field is known as the catenary.
Is there known an expression for the curve of a hanging chain on a planet of mass $M$ which ...
3
votes
1answer
740 views
Statics question: When do I need to find support reactions?
We're finding forces (and whether they're in tension or compression) using the Method of Joints and Method of Sections. I don't understand why sometimes it's necessary to find the support reactions, ...
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4answers
2k views
Upward force on a object at rest
Is there an upward force on a object at rest? If yes, where does it come from?
2
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2answers
260 views
What is the shape of a clamped bent bar?
How would I figure out the Cartesian graph that describes a bar clamped flat for a length on one end with downward force being applied to the other?
I have an idea that the bar will try to average ...
3
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5answers
508 views
How much force would be necessary to hold a 6-foot steel staff weighing 20 lbs from one end of it, parallel to the floor?
This isn't a homework problem. I'm asking cause I'm wondering how strong a person would have to be to pull it off. Their arms would be extended, both hands gripping the staff at one end, and the staff ...
5
votes
2answers
562 views
What determines the (minimum) angle at which a domino falls over?
Dominoes, when placed upright, remain that way. Sometimes, even if you tip them a little bit, they will go back to their upright position.
However, if you tip them too far, they will fall over.
...
