Questions tagged [statics]

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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1answer
2k views

Calculate weight needed to balance a beam

I have found many sources to determine the weight or force needed for a balance moment, but not one that included the weight of the beam as a variable. I assume this is a very simple equation. Please ...
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155 views

How is this system in equilibrium? [closed]

So, after mathematically calculating the answer I found it to be zero. But my teacher says I don't have to do the calculation as this system is in equilibrium and the initial acceleration is zero. But ...
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2answers
541 views

Two sliding blocks and friction [closed]

I was doing a practice problem in prepping for a midterm and then numbers that I got just seem implausible. I know that they are the 'right' answers, I'm just not sure if this situation could exist in ...
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1answer
246 views

Static analysis of rigid bodies in 3D [closed]

How to calculate torque due to gravity of a 3D linkage mechanism? I am performing a static analysis of a Baxter Robot arm. How to calculate the torques at each of the joints ?
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72 views

Can this really happen?

I saw an interesting image , would it fall down or stay in stationary?
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3answers
348 views

Why exactly is the pressure an object experiences at a given depth in a fluid?

I am currently trying to work through why an object with smaller density than the fluid it is in floats upwards. I know that the object experiences pressure in all directions because it has moved ...
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6answers
190 views

Which way will the scale tip? [duplicate]

This problem has bothered me for quite some time and I can't solve it. I have even tried to make a construction, but it sometimes tips to the left and sometimes tips to the right :). When we submerge ...
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3answers
274 views

How does torque work?

Why can we assume the the net torque is equal to zero when we pick one of the points as the axis of rotation. For example if we selected the left leg of the table for the axis of rotation why can we ...
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170 views

Counting experiment and standard error

I have a counting experiment: Let's say I have N identical bees. I take one of them, expose it to $\gamma$-radiation and look if it has died or survives. If it survives, I count it as 1 count. If it ...
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1answer
490 views

How to calculate the maximal weight that a cable can support? [closed]

Exercise: Exercise from Theory and Problems of Physics for Engineering and Science. In the crane here the boom is $3.2 \text{m}$ long and weighs $1200 \text{N}$. The cable can support a tension of ...
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0answers
31 views

How to consider another Cartesian axis?

Well, I solved the problem. The point is that I used a x and y axis with x parallel to the inclination of the box, but I wanted to think differently, if one considers the y axis itself containing the ...
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1answer
412 views

Basic Static Equilibrium of a rigid body

I'm trying to understand static equilibrium in 3-dimensions, but I feel like I should understand it in 2-dimensions first let's assume we have a rock with inhomogeneous density (black rectangle) with ...
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3answers
514 views

Under what condition would I fall off a cantilever chair? [closed]

So this question is nagging at me and after many rounds of searching I still can't figure it out. I want to know is how load is distributed through a cantilever chair. Under what circumstances would a ...
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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. ...
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1answer
492 views

How to make a free body diagram of a lever?

So this is what we are working with: Basically, the spring and the lever are used to press in the plug (part no 2). I need to find the force that is acting upon the welding (I painted it in red). Now ...
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2answers
7k views

Why is skidding considered kinetic friction when braking on a car?

So according to my textbook applying the brakes hardly to essentially lock up the wheels causes skidding which is kinetic friction so the breaking distance is longer. However, if the brakes were "...
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What is the difference between Quasi static and Dynamic simulation?

I'm a newbie in Physics, I read some papers in bio-mechanical that model human joint motion, some of them are modeled using Dynamic, while others using Quasi static. All I know so far is that in Quasi ...
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1answer
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Where does the formula for bending of a rod come from?

For a rod of length $l$, breadth $b$, depth $d$, and Young's modulus $Y$, the rod's center of mass comes down by a distance $\delta$ when a weight $W$ is hanged from its center $$\delta = \frac{Wl^3}...
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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 ...
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1answer
58 views

Static geometry problem [closed]

Why is the force Nb has triangle of height a and base 2r. Why is not height 2r and base a?
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1answer
494 views

direction of resultant moment about axis using scalar and right hand grip rule? [closed]

From the picture posted, this question is taken from my solution manual. I understand that using vector method of finding the resultant moment. I also know when we use scalar with right grip rule to ...
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2answers
439 views

Why are truss members two force members and why are the forces directed along the axis of the member?

In Hibbeler's book, Engineering Mechanics: Statics, on pages 264-265 it is mentioned that two assumptions are made in the design of a truss: All loadings are applied at the joints The members ...
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1answer
710 views

David Morin's question: Mountain climber [closed]

This question is from Introduction to Classical Mechanics, David Morin. A mountain climber wishes to climb up a frictionless conical mountain. He wants to do this by throwing a lasso (a rope with ...
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2answers
511 views

Rigid body equilibrium word problem

In my 100-level university physics course, we are just starting to touch on rigid bodies and tension. While I am fairly certain that I approached this the right way, I would appreciate if someone ...
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2answers
296 views

Forces on a ladder leaning against a box

My question is based on the following problem: A ladder of length $l=3\mathrm{m}$ is leaning against a box with height $h=2\mathrm{m}$ so that the angle between the ladder and the ground is 60 ...
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1answer
657 views

Problem regarding Buoyancy forces and Archimedes principle

A thin-walled container of mass $m$ floats vertically at the separation surface of the two liquids of density $ρ_1$ and $ρ_2$ . The whole mass of the container is concentrated in the part of height $...
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3answers
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A simple (?) problem of static equilibrium

A question on the site made me consider this simple problem, that unexpectedly seems to be indeterminate. Consider a perfectly rigid, homogeneous bridge of mass $m$ with three pillars, one placed ...
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6answers
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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 ...
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3answers
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How $4$ forces achieve equilibrium? [closed]

Two identical uniform rods, each of weight $W$, are hinged together to form a structure which is resting on a rough floor as shown. If the reaction forces acting on the structure by the floor are $...
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1answer
65 views

When will the block lift up the front wheel? [closed]

Here is my problem: the luggage is being pulled with force $T$ at an angle $\theta$. I'd like to know when the front wheel will lift up. How do I even start? Before lifting it up, all I know is that ...
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1answer
108 views

Calculating forces in stucture [closed]

I know how to find the reaction at a A and E and they worked just fine with me as external forces. But I am not understanding how to find the forces at joints B and D, what is the approach ?
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Find agle for equilibrium [closed]

If someone could help I'd be greatful. The data of the problem are: Mass of the 2 blocks : 2Kg each Mass of the ring: 4*Pi Kg Find the angle theta. I have found that the normal at the floor is : 4g(...
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1answer
721 views

Moments of a barbell

For a barbell with 1. heavier weights near the centre heavier weights near the end (invert the order of the weights in the picture below) Will the barbell with heavier weights near the end be ...
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1answer
229 views

Reaction forces in pyramid stacking of steel coils

I was tasked with solving this problem at work as we are out of coil holders and we bought 140 coils and need to stack them asap. Companies that make the storage holders are on back order for several ...
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1answer
839 views

Leaning ladder reaction force

Shouldn't the reaction force by the ground act along the direction of the ladder? under what conditions will it be along the ladder. What causes the direction of reaction force to not act along ...
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1answer
202 views

Moment of a force convention?

Two forces P and Q pass through a point A which is 4 m to the right of and 3 m above a moment center O. Force P is 890 N directed up to the right at 30° with the horizontal and force Q is 445 N ...
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2answers
844 views

Solving a problem using Newtonian mechanics and D'Alembert principle

yI have to solve that problem with two methods (applying Newtonian mechanics and the D'Alembert principle. The problem consists in two balls inside a spherical cylinder, it consists in determine the ...
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1answer
104 views

Force couple simplification

How is it possible to add all the force components to find resultant when forces are acting at different points on the body?
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2answers
264 views

Equilibrium of a tower of 2-d blocks

In the image below, All the blocks are frictionless & identical with side of unit length, height $h$, weight $w$ & center of gravity at their geometric centers. The 2 lowest blocks are on ...
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2answers
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Vehicle weight distribution [closed]

I've been creating a 2D (above view) vehicle simulation as a hobby project, and (as is often the case) a problem which I assumed would be simple has turned into the sticking point of the project. ...
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2answers
692 views

Influence of couple-moment's position on bending moment diagram

The moment of two equally opposing force would create a couple-moment. Since the couple-moment value is invariant to the point considered to calculate the couple-moment, I can replace the two equally ...
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2answers
582 views

D'Alembert's principle : static equilibrium of two inclined rods in frictionless rectangular well [closed]

Two rods of length $2a$, masses $M$ and $m$, are in static equilibrium inside a rectangular well of dimensions $a \times 2a$. What are the equations that fix $\phi$ and $\psi$? (One has a "mechanical" ...
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1answer
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Find the potential between two non-conducting parallel planes [closed]

How would I solve the following? Two uniformly charged, infinite, nonconducting planes are parallel to a yz plane and positioned at x 50 cm and x 50 cm. The charge densities on the planes ...
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2answers
454 views

Static Equilibrium with 3 tensions [closed]

Hey guys, for the question that asks you to determine the tension in all 3 cables I am kinda confused. My teacher said the 2nd tension opposes gravity, so it is equal to gravity. then you can equate ...
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1answer
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Estimate the reaction force on each leg of a 4-legged table

Assume you have a table with four legs with a weight placed somewhere inside the boundary created by the legs. The task is to determine the reaction force at each leg. Here are the problem ...
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1answer
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How much would this shelf support? [closed]

Consider the following scenario: I am would like to mount a shelf to my wall. To support the shelf, I am using two drywall anchors, which each are rated at 50 lbs. If each anchor is placed on one end ...
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1answer
54 views

Does it make sense to compute moment of force about any axis?

This Wikipedia article gives that If the unit vector along the axis is $e$, the moment of force about the axis is defined as $$M=e \cdot M = e \cdot (r \times F)$$ Then gives an example which I ...
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1answer
194 views

Finding normal reaction [closed]

In the given figure, find the normal reaction applied by surface OB and OC on spherical mass m = 10 kg as shown
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1answer
522 views

How to find static friction coefficient and the applied force's angle of inclination with a horizontal plane?

Okay so I have this weird problem in my statics book that wouldn't come to a solution no matter what I tried. It states the following: A body of weight $4$ kg.wt is placed on a horizontal rough ...
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1answer
157 views

Differences between these four branches of physics

I am wondering what are the main differences between these four branches of physics: Statics, Kinematics, Dynamics, and Kinetics? And whether the following relationships are correct or not? Statics: ...