The statics tag has no wiki summary.
3
votes
2answers
42 views
Why are some jenga pieces easier to remove than others?
Jenga is a game place with wooden blocks stacked on top of one another in an alternating pattern. Players take turns removing blocks from any layer and placing them on top.
As the game progresses ...
0
votes
0answers
21 views
The stress in copper and steel parallel compound members [closed]
Came across this question and just needed abit of help undertanding how i should go about this question
I have also attempted to solve it to the best of my ability but im stuck.
A concrete column of ...
2
votes
1answer
56 views
Tension in a closed loop around an object, carrying stuff
Sorry when this sounds like a first year physics homework question, but it's actually not. It arose during a discussion regarding safe practices for rock climbing anchors...
So here we go: Imagine ...
12
votes
5answers
1k views
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 ...
2
votes
1answer
81 views
Statics of Rigid Bodies — Can there be two possible solutions?
I've been working on a question and there seem to be two possible solutions. My own solution does not match the one given in the book. However, after resolving forces and taking moments with both ...
3
votes
3answers
88 views
Does a cross really have a smaller area moment of inertia than a square of the same area?
I need to calculate the area moment of inertia of a cross for a homework assignment. The cross is a symmetric plus sign:
_
| |
|== ==|
| |
-
...
0
votes
1answer
86 views
Problem solving moments in equilibrium
Two straight ladders, AC and BC, have equal weights $W$. They stand in equilibrium with their feet, A and B, on rough horizontal ground and their tops freely hinged at C. Angle CAB = 60$ ^o$, angle ...
4
votes
1answer
85 views
Application of Archimedes Principle
A candle is floating in a liquid placed in a container. The container is a cylinder of diameter $D$, and the candle is of width $d$. ($D>d$) The height of the liquid from the bottom of the ...
0
votes
1answer
31 views
Find the bending moment of a pole attached to a moving block
I'm having trouble with the following problem.
What I've done so far:
x-y is the usual coordinate system.
$a=\frac{F}{m}=\frac{800}{60}$ and the y component of this is $a_y=a\sin{60^\circ}$.
To ...
0
votes
0answers
72 views
Tension $T$ in cable [closed]
Calculate the tension $T$ in each cable, as well as the magnitude and direction of the force exerted on the strut by the pivot in each case mostrados.En systems, w is the weight of the suspended box, ...
1
vote
1answer
127 views
Cylinder rolling down an inclined plane held by a string
A cylinder of mass M and radius R is in static equilibrium as shown in the diagram. The cylinder
rests on an inclined plane making an angle with the horizontal and is held by a horizontal string
...
1
vote
1answer
72 views
Force analysis on truss
I am reading a book on fundamental physics for mechanics. There is a truss shown in the figure. A train of mass $M=56$ ton is resting at the middle point of AC, ignore all the mass of truss and rails. ...
0
votes
1answer
54 views
Statics Moment Diagram
I am having troubles converting my shear diagram into a moment diagram. Either I am doing something wrong or MasteringEngineering is incorrectly marking it wrong. Anyway here is the problem/correct ...
5
votes
3answers
221 views
Force between two charged rods?
Suppose that we have two rods of length $l_1, l_2$ connected at one end but free to rotate. These rods have charge density $\lambda$ uniformly distributed, so the total charge of rod $i$ is $\lambda ...
0
votes
0answers
27 views
How do I minimize the the stress created by fore-aft forces?
My friends and I are designing a bench press spotter. Essentially, when the user needs help lifting the barbell due to muscle fatigue, an arm on each side of the user raises to provide assistance. ...
1
vote
2answers
100 views
Additional mass of block on inclined plane
I would like some help in solving this problem.
Height is 15 cm , base is 88 cm
My attempt:
$$(119.3 + m)(\sin(\theta)) = (88*9.8)$$
$$ 15^2 + 88^2 = 89.269^2 $$
$$ \sin^{-1} = 15/89.269 $$
$$ ...
0
votes
1answer
430 views
Calculation of a bending moment
I'd like to calculate the bending moment of a cantilever, fixed at its base, and submitted to a certain stress on a specific spot, but I can't find the proper definition of this bending moment (first ...
0
votes
0answers
151 views
How to solve fixed-fixed beam with finite difference method?
What equations to use on this system to form a matrix $A$ with dimensions $[n,n]$ and load vector $q$ with dimension $[n]$ ? I am trying to get vertical displacement $w$.
$$w = A^{-1}\times q$$
...
1
vote
0answers
54 views
How can I calculate all of the tensions in the cords? [closed]
I have been stuck on this problem for the last half, and to be honest I don't even no where to begin. I'm being asked to calculate all of tensions for the cords. I know I'm supposed to use $\cos$ to ...
3
votes
0answers
170 views
Shape of a string/chain/cable/rope?
The height of a string in a gravitational field in 2-dimensions is bounded by $h(x_0)=h(x_l)=0$ (nails in the wall) and also $\int_0^l ds= l$. ($h(0)=h(l)=0$, if you take $h$ as a function of arc ...
3
votes
2answers
205 views
Bowling ball on a rubber sheet
After reading a layman's guide to general relativity, I began to wonder what shape a bowling ball on a large rubber sheet would produce. For simplicity, I would like to assume that Hooke's law applies ...
0
votes
3answers
133 views
Doubts with levers
I'm studying for a test of static rigid body and I'm having doubts on how to solve problems involving levers with weight.
If I have, for example, a lever 10 kilograms and 3 meters long and one support ...
1
vote
1answer
431 views
Solving a Statically Indeterminate Truss with Energy Equations (Tricky)
Okay, first off, I know that there is a very similar problem about statically indeterminate trusses here, but my problem was a bit different and I didn't know how to adapt the answer for that problem ...
0
votes
1answer
622 views
How to calculate the supporting force for a cantilever beam? [closed]
How do I find the supporting force $R_A$ and the moment $M_A$?
Should I use the sum of moments or?
0
votes
1answer
186 views
Trying to understand the tension in a spring with two weights attached [duplicate]
Possible Duplicate:
Why I think tension should be twice the force in a tug of war
For (A) in this image, I would think the tension should be should be 2mg.
However, my book says the ...
0
votes
1answer
211 views
Can I use Newton's second law to solve what seems to be a torque problem?
The Problem:
An 8-m-long beam, weighing 14,700 N, is hinged to a wall and supported by a
light rope that is attached 2.0 m from the free end of the beam. If the beam is
supported at an angle ...
2
votes
1answer
93 views
Can structural trusses in centrifuges be helpful at all?
Imagine a rotating space station for the purpose of creating artificial gravity. Generally, such a space station is portrayed as a ring or a cylinder. Images of these space stations often have lines ...
4
votes
1answer
735 views
Solving a statically indeterminate truss
I'm trying to solve the statically indeterminate truss shown below and I'm having a little trouble.
$H$, $P$ and $\beta$ are given. The material is aluminum (density is 2700 ${kg/m^3}$) and has a ...
0
votes
1answer
139 views
Relationship between torques and centre of mass or centre of gravity [closed]
1) A wardrobe is $2$m high and $1.6$m wide. When empty, it has a mass of $110$kg and its centre of gravity is $0.8$m above the centre of its base. What is the minimum angle through which it must be ...
1
vote
1answer
60 views
Force in tetrahedron edges
I am looking for a formula that enables me to calculate the force in a tetrahedron edge such that it relates $F_b$ with $F_z$ through the beam thickness and length. I have the following assumptions:
...
3
votes
0answers
90 views
Obtaining point of application of Ground Reaction Force with use of a hyperstatic load-cell array platform
I'm looking for the theory of an experiment that is giving me a hard time to perform.
I have an instrument composed of a rigid horizontal square plate rigidly supported under each corner by a ...
3
votes
1answer
561 views
If 1 screw can support 120 lbs, how much weight can 25 screws support?
While this is mainly about my personal home improvement project, I figure this would be a good opportunity for some of you to apply your physics skills to a real-world situation.
My situation is ...
-1
votes
1answer
259 views
Internal forces in a truss and its geometry
I'm to work out the internal forces in a truss, but I can't get my head around the geometry of the truss itself. I'm starting to think there may have been information on the diagram which I missed. ...
3
votes
2answers
859 views
Calculating torque adjustment for offset of pivot point
I'm trying to figure out how much to adjust torque, on a torque wrench when using an extension that offsets the pivot point. See this calculator for a diagram of what I'm talking about:
The trouble ...
0
votes
1answer
275 views
Torque and equilibrium
I am a little stuck on the concept involved in part b) of the following problem:
A $5 m$ long road gate has a mass of $m = 15 kg$. The mass is evenly distributed in the gate. The gate is supported at ...
3
votes
1answer
354 views
Understanding moments as forces?
I was watching this lecture on analysis of stress for mechanics of materials. At time 7:20, the lecturer says that in equilibrium, the sum of forces and "moments" in each direction (x,y,z) must be ...
0
votes
1answer
326 views
Calculating torque in a structure
I posted this on math stack exchange but realize it is more a physics question.
I have a structure which is set up as shown in the image. A weight hangs from point A with mass $m$. Joint B is free ...
2
votes
1answer
525 views
Relationship between balloon size and pressure
I see numerous websites talking about how a small balloon is at higher pressure than a big balloon. This is a fun counter-intuitive factoid... unless it isn't a fact at all.
Young-Laplace gives
$$T ...
2
votes
1answer
274 views
Why does the beam in a weighing balance get tilted proportional to the weights added to each pan?
I'm talking about a beam balance(a simple weighing balance with a beam and two pans hung on either side)
As answered in a previous question, the beam comes back to the original position when one ...
0
votes
2answers
178 views
Hanging a Hammock
I have a hammock that I want to hang using a tree on one end and a wooden post set in a bucket of cement on the other end.
How would I determine how heavy the cement needs to be so that it would ...
2
votes
2answers
853 views
Angles on swing sets
I'm building a swing set for my children. All of the designs I've seen involve building two A-frames and connecting them at the top with a crossbar/beam from which hang the swings. The A-frames are ...
3
votes
3answers
190 views
What is a “Center Of Mass” issue of a Gorillapod?
I read somewhere that a Gorillapod may have "Center Of Mass" issues when used with the long lenses.
So, I wish to understand what is a "Center Of Mass" issue?
I have to clarify that I am NOT a ...
0
votes
1answer
290 views
Hinged bridge statics problem
For part (a), is the normal force by the hinge on the bridge at an angle or is it horizontal?
For part (b), I know how to resolve forces horizontally and vertically, and to take torques about the ...
1
vote
1answer
449 views
Calculating mass of object by lifting edge
Assuming a solid rectangular plate, hinged along one edge. How does one calculate the mass of the plate if the force necessary to lift the opposite edge is known?
2
votes
1answer
199 views
Poisson effect formula for large deformations
English Wikipedia in the Poisson's ratio article gives an equation for large deformation:
$$
\frac{\Delta d}{d}=-1+\frac{1}{\left(1+\dfrac{\Delta L}{L}\right)^\nu}
$$
I couldn't find any reference ...
2
votes
2answers
456 views
How do you weigh a box on a scale whose limit is too low?
As you will see I know nothing about physics and after being asked to solve a physics problem in a recent interview wanted to ask it of professionals and see what the response would be:
I have a set ...
0
votes
1answer
207 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
286 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
votes
3answers
709 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
votes
1answer
361 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 ...
