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

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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, ...
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26 views

Statics and 3-D Equilibrium of Rigid Bodies [closed]

and Thank You for viewing this problem! I am new to Stack Exchange, I never heard about it until a friend recently introduced me to it.. The problem: The bent rod ABDE is supported by a ball and ...
1
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2answers
225 views

Determining the neutral axis of an I-shaped cross section with dissimilar materials

Determine the neutral axis of the I- shaped cross section with dissimilar materials. The top rectangle of the cross section is made out of aluminum and the second and third part are titanium ( these ...
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3answers
789 views

How to determine direction of forces in a static problem?

I am consistently getting this wrong. To me, in the picture below, it would make sense that the structure would be pulling downward, and the cable BD would be pulling upward - thus the system is in ...
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1answer
22 views

Torque in a 2-segment robot leg

I have a (hypothetical) robot with two legs, each with 2 segments, with a joint at the body of the robot and in the 'knee' of each leg, as in this (poorly-drawn) diagram: (Sorry about the quality and ...
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1answer
32 views

Weighing with One-Foot Scale

I stand with left foot on a scale and the other on a piece of effectively incompressible material at the same initial height at the scale's top surface. The weight shown is WL. I repeat with right ...
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2answers
49 views

Does the distance two weights are from you alter the difficulty of lifting them?

If I am weightlifting and I choose to do the deadlift, does it matter how far away from me the weights are on the bar, given that they are equally distance from me on both sides. E.g. I am deadlifting ...
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1answer
112 views

How to calculate the supporting force exerted by a stationary object (cupboard) and support (brackets) for it?

I have a wall mounted Stuva Ikea cupboard, which measures 60x64x30cm. The base is 64x30cm. It is already supported by 2 holes at the back base, (64x60cm). But I need to add in L shape brackets ...
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6answers
2k views

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 ...
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3answers
3k views

How do I find the tension in additional strings in this problem? [closed]

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
168 views

How is weight distributed when legs are astride?

Is there a simple and quick formula to find the weight (the force acting) on each leg, especially when legs are astride and they are not equally stretched? (or, better) not equally distant from the ...
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3answers
162 views

What is the equation for the tension on the ends of a cable suspended at different heights?

I'm looking for an equation to find the tension on the ends of a cable suspended between two poles (one higher than the other) with no load but the cable itself. I determined that the tension would ...
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1answer
394 views

Finding the mass of bed/Patient [closed]

One of my friends has a problem and we don't know how to get this done, We want to to know the mass of a patient who is laying on a bed. One scales was put under the foot of a bed and weighed 232kg ...
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1answer
28 views

Finding directions of the internal forces within a freely jointed rigid object?

Consider the the following problem: Here is a force diagram showing the situation: For part (i) Taking moments about $B$ for $BC$ gives $84.5Lcos\beta=2LT$ So $T=39$N For part (ii) Resolving ...
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1answer
120 views

Forces acting on two balls in a jar [closed]

Consider the following situation: Two balls are inside a jar with diameter $D$. The balls are uniform in mass and both have the same diameter $d$. Express the forces that acts at the colored dots ...
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3answers
85 views

Topple a mass standing still

Consider the following situation: This is taken from an example from my book with a solution. The box weight is $W$ and the coefficient of friction between the floor and the object is $\mu$. What ...
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2answers
27 views

A statics problem to find minimal friction

consider the following: I need to find the minimal coeeficient of friction $\mu _{min}$ so that both recatngle boxes would remain static. The lower angle in the triangle is $2\alpha$ as indicated. I ...
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1answer
181 views

Massive ropes and tension

Consider the diagram bellow, a massive string hanging in equilibrium My question is this: Can we take any 2 random point on the rope, say A and B and then use $\sum F=0$ on the rope between them: ...
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0answers
40 views

Torque of person on bridge [closed]

Consider a 10 meter bridge that weighs 500 N supported at both ends. A person who weighs 750 N is standing 2 m from the end of the bridge. What are the forces $F_a$, $F_b$ holding the bridgeup at ...
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1answer
62 views

Statics with ladder and wall

A uniform ladder of mass m and length L rests against the wall. The coefficients of static friction between the floor and the ladder and between the wall and the ladder are equal to each other (μ). ...
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1answer
91 views

How do I know which force to use in moments calculation?

I'm working on some Statics problem, with the method of joints, etc and for all of them, we use sum of moments = 0. However, I'm very confused about which forces I should use to find the sum of ...
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1answer
113 views

Hanging a brick free over an edge by stacking them

National Geographics TV has a series called "None of the above". In one episode the presenter shows that by stacking 4 bricks (here shown as 'xxxxxxxx') you can have one of the bricks completely hang ...
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1answer
88 views

Relative strength of a dome

Is there a rough way to determine how the height of a dome affects the load that dome could support? For instance, assuming the bases of two domes are 24" in diameter, and one dome is 2" high while ...
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1answer
45 views

Sign of gravitational force

I'm reading Lanczos's The variational principles of mechanics, and on pp. 80-81 there is an example involving a system made up of $n$ rigid bars, freely jointed at their end points, and the two free ...
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0answers
496 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 ...
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1answer
83 views

Finding the Shape of a Hanging Massive Wire

This came from a physics wave book. I have a static, massive wire on the x-axis, with a y-displacement due to a force per unit length $F_y$. I start with the equation $F_y = ...
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1answer
177 views

Calculating stiffness of a beam of non-constant cross section

I am considering a paraboloid shape which is fixed at its base and is being compressed downwards. I am trying to find its stiffness so I can calculate how much it deforms. When I attempt to do this I ...
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2answers
154 views

Static equilibrium question [closed]

I was doing some static equilibrium problems and I came across this problem which should be easy to solve, but is posing quite a challenge. I want to point out that this is not homework, just plain ...
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0answers
62 views

Friction force problem for a 4 wheel drive Car [closed]

The car is a 4 wheel drive in equilibrium, the car doesn't touch the ground with the front wheel (A) but is in contact in B with the sidewalk (the sidewalk has a hight equal to $h$), the friction ...
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1answer
37 views

Optimal placement of support joist under shelf

Assume an ideal board, supported by two joists. Where should those two joists be optimally placed? Instinctively, I'd say at somewhat less than 25% and somewhat more than 75% of the extend of the ...
0
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2answers
92 views

Centre of mass and objects tipping [closed]

In this picture if the only parts of an object in contact with a surface are the lines AB and CD am I right in saying that the centre of mass has to be in the area enclosed by ABCD (as shown). I ...
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1answer
253 views

Mechanics question - ladder leaning against a wall

I am struggling with part a) of this question: Here is the solution: In part a) they prove that $F \leq \mu R$ is false for this system. So as $F$ is neither less than nor equal to $\mu R$ it ...
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0answers
97 views

Truss Analysis with multiple moments creates linear combinations

So in my engineering statics course we have been doing a great deal of work with trusses and machines, and a part of the physics behind it has really been confusing me. Just as a note, I also have ...
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4answers
2k views

Blocks stacked on an incline connected by rope around pulley

Two objects A and B, of masses 5 kg and 20 kg respectively, are connected by a massless string passing over a frictionless pulley at the top of an inclined plane, as shown in the figure. The ...
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1answer
432 views

A Bar Suspend by Two Wires - PHYS I HW [closed]

A nonuniform horizontal bar of mass $m$ is supported by two massless wires against gravity. The left wire makes an angle $ϕ_1$ with the horizontal, and the right wire makes an angle $ϕ_2$. The bar ...
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0answers
19 views

The magnitude of the resultant? [closed]

The two structural members, one of which is in tension and the other in compression, exert the indicated forces on joint O. Determine the magnitude R of the resultant R of the two forces and the angle ...
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2answers
423 views

Calculating axle load in cargo container (pics are included)

I'm current developing cargo loader software, but i have a little challenge with calculating load for each axle when a cargo is placed on container. I know that all axles will be affected (the nearest ...
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1answer
315 views

Given moment about a pin and a roller [closed]

sorry to ask, have not been a able to find a similar question to mine. For this problem, given moment $M_2$, distances $a$ and $b$ My reasoning is that we have two support reactions and points A and ...
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1answer
250 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)?
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1answer
111 views

Moment around a point in a frame

Note: Both diagrams are 2d(they might look 3d because I drew them manually.) I have a prismatic frame that looks like this: I made a section on the half of the first pillar(the red line represents the ...
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2answers
453 views

How do I find the tension in the cable from this problem? [closed]

I am trying to find the tension of the cable but I don't know what to do.
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1answer
108 views

Moment of weight of leaning beam

Having trouble with a FBD moment. The problem is: How big can the force couple C (looks like a G in the pic) be in order for the disk to not spin? The disc has mass m and the beam also has mass ...
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1answer
136 views

Weird assumption in free body diagram problem

The assignment is to eventually calculate the forces on the BD beam of this picture: My issue is that on the solution sheet, the professor drew a free body diagram (FBD) for just the beams, with ...
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2answers
123 views

Friction acting on mass on string

Assume we have some stationary point mass that would slide, if not for some coefficient of friction, along a light, inextensible string, attached to two points at different heights. Considering ...
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1answer
853 views

Tension on pulleys Physics Question [closed]

Collar A is connected to a 50lb load on a frictionless horizontal rod. Determine magnitude of P to maintain equilibrium when x=4.5. Im confused on the concept of Tension I originally got the ...
20
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6answers
4k 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 ...
4
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3answers
303 views

Moment of Inertia, why $r^2$and not $r$?

So my engineering mechanics book includes a brief discussion on area moments of inertia. Unfortunately, the ensuing chapter is predominately computational in nature. I don't have a thorough grasp of ...
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3answers
1k 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 ...
2
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1answer
93 views

Can all systems be put in equilibrium?

I'm in a first year statics course. We have spent the whole semester solving for forces and moments so that the system is in equilibrium. When we are given a system, we immediately begin solving for ...
2
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2answers
282 views

A man pulling himself up on a platform

Consider the following image: Is it possible that the man pulls himself up (suppose the weight of the platform is negligible), or just lift the right part of the platform up? How to analyse this ...