Analysis of a system of bodies where all forces are in balance and there is no motion relative to a chosen reference frame.

learn more… | top users | synonyms

0
votes
1answer
215 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 ...
1
vote
1answer
2k 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 ...
-2
votes
1answer
648 views

Shear Flow corresponding to Eccentric Shear Force of a Closed-section Beam (Structural Analysis - Mechanics)

Been stumped with this question for way too long... its a beam with a thin-walled rectangular cross-section, and a shear force is acting at a distance from the shear center. I know my decomposition of ...
1
vote
2answers
743 views

Force analysis on truss [closed]

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. ...
6
votes
3answers
1k 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
42 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
1answer
298 views

Choosing the right point when calculating moments

A body is composed of two straight pins that are joined at a right angle. They have lengths $a$ and $b$ and the mass per unit length is $\rho$. When the body is balanced on a flat surface, as shown, ...
1
vote
2answers
186 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
735 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
416 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
183 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
706 views

Shape of a string/chain/cable/rope/wire?

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
355 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
354 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
1k 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
2k 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
1k 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
1k 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 ...
3
votes
1answer
189 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 ...
5
votes
1answer
2k 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 ...
1
vote
1answer
183 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
152 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 ...
5
votes
1answer
4k 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
481 views

Internal forces in a truss and its geometry [closed]

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
5k 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
550 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 ...
4
votes
1answer
921 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
560 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
3k 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 ...
3
votes
1answer
2k 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
556 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 ...
3
votes
3answers
8k 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 ...
0
votes
1answer
367 views

Using Moments to influence the thickness of beams in structure?

Are moments relevant to the thicknesses of beams in a structure (ie. the larger the moment the thicker the beam)?
5
votes
5answers
8k views

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 ...
3
votes
3answers
274 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
517 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
2k 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
450 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
2k 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 ...
-1
votes
1answer
326 views

Bridge Trusses? [closed]

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
766 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
4k 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
734 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 ...
3
votes
0answers
2k 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
votes
1answer
271 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
178 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
355 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
vote
1answer
471 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 ...
1
vote
3answers
1k views

Statics software for structural engineering [closed]

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
votes
2answers
6k 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: ...