Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange
Join us in building a kind, collaborative learning community via our updated Code of Conduct.

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

1
vote
0answers
17 views

How can I apply statics to a (real life situation) hanging white board?

Im curious what solving a statics problem of a hanging white board can tell me. My whiteboard recently fell because the sticky hook peeled off the wall. By finding the tension forces in the string ...
2
votes
1answer
42 views

Is there a name for this phenomenon?

Imagine I have a cylindrical pipe closed on both ends with lids. I fill it with sand and compress the sand tightly. Now I hold the cylinder vertically and remove the bottom lid. The sand will counter ...
-2
votes
0answers
34 views

How to determine the tensions in a particular rope and two blocks arrangement? [on hold]

How do I find out the tensions $T_1$, $T_2$, $T_3$, and $T_4$ in the arrangement in which two blocks of 1 kg and 2 kg are hanging through a rope which is making an angle of 45 degree and 60 degree ...
0
votes
1answer
29 views

Tipping angle of a box

how do you calculate the tipping angle of a box? That is the maximum angle a which a box can reach before tipping over. help, please!
49
votes
4answers
14k views

Why is the shape of a hanging chain not a “V”?

From Wikipedia: To answer this question: "What is the shape of a chain suspended at both ends?" we can use the variational principle that the shape must minimize the gravitational potential energy. ...
-1
votes
1answer
105 views

3 people carry a log of wood, which one is carrying the most weight [closed]

I saw this on a youtube video. The answer is that the one in the middle is carrying 25 % more than the other two. Can someone explain this?
0
votes
1answer
36 views

Varignon's theorem (Principle of moments) failure?

Varignon's theorem states that "If many coplanar forces are acting on a body, then the algebraic sum of torques of all the forces about a point in the plane of the forces is equal to the torque of ...
1
vote
1answer
36 views

A question about temperature in the concept of a macroscopic statistical-mechanical system

I recently have come across a question while working on Statistical Mechanics. The question itself was quite straight forward (no this is not a "do my homework" question in case you were wondering) ...
0
votes
2answers
50 views

Power in 1st Gear

The max power an engine puts out is what determines the max speed a car travel at right, obviously it's more nuanced than that because there are losses in the drive train, and the shape of the car ...
1
vote
2answers
50 views

Finding the equation of a chain hanging between two points

Say I have a connected at either end to two points, $A(x_A, y_A)$ and $B(x_B, y_B)$ of length $l$, where $l \leq \sqrt{(x_B - x_A)^2 + (y_B - y_A)^2}$, how would I go about finding an equation of its ...
1
vote
1answer
58 views

Conditions for Static Equilibrium of Rigid Body [duplicate]

When there are forces acting on a rigid body, the two conditions that has to be satisfied for the body to be in static equilibrium are: 1. The sum of all forces must be zero (translational equilibirum)...
1
vote
1answer
89 views

Work done in lifting a object from underwater if it displaces $W'$ of water? [closed]

A spherical shot of W gm weight and radius r cm, lies at the bottom of cylindrical bucket of radius R cm. The bucket is filled with water up to a depth of $h\,\mathrm{cm}$ $\left(h > 2r\right).$ ...
-1
votes
1answer
93 views

Why can't a pyramid stay balanced on a vertex? [duplicate]

A pyramid, such as a tetrahedron/3-simplex, or any other isohedron, falls from some height and lands on a vertex. It will eventually end up with a face to the ground. Why can't it stay balanced on a ...
2
votes
2answers
57 views

balancing a weight on a table without tipping over

I have a statics problem. Here is a model for a table: a circle of radius 1.5 ft a pole in the center a base in the shape of an X. I place a weight on the table on the edge. How much weight can ...
0
votes
1answer
35 views

Equation to model change in leverage point

Is there a mathematical model for the situation below? First, I want to know how much force I would need to lift this block some distance using this wooden board. The block is situated against a wall ...
0
votes
0answers
49 views

How do bicycle pedal forces resolve?

If you're standing on a stationary bicycle, with pedals at 3 and 9 o'clock, how do the forces resolve if you shift your weight over the rear pedal? Most weight is on your back foot. Since your front ...
0
votes
1answer
108 views

Static equilibrium- when do you use forces and when do you use torques?

I'm working on an answered physics question in the book but I'm having trouble understanding why the problem could be solved by setting net torque equal to 0 and not net force. You are asked to find ...
0
votes
1answer
32 views

Rotating a cube to the verge of tipping over [closed]

The problem: A $100\,\mathrm{kg}$ cubical box lies on the floor. A child pushes horizontally at the top edge. What is the magnitude of force to put the box on the verge of tipping over, given that ...
0
votes
0answers
15 views

How does a balancing machine works? [duplicate]

Suppose I have a balance . Both of its pans have same mass kept on them and it is balanced with both masses at same height . I pull down one of them to some height. Will it come to its original ...
0
votes
1answer
29 views

How to solve problem with homogenous ball at equilibrium? [closed]

The answer according to solution manual: $F_A=566N F_B=283N$ I am not asking for you to solve this exercise, this is not a place for homework, I know. I need help how to think so I can solve this ...
0
votes
1answer
38 views

Does a car effectively become heavier the faster it moves?

Just for clarity, I'm not asking in relativistic terms. Assuming the engine's pistons aren't horizontally opposed, would the vertical force of the pistons move the car downward? Or would it not ...
-2
votes
1answer
43 views
0
votes
0answers
6 views

What stresses should be considered to determine the effective stress and FOS?

This question I tried to solve by considering the torsional shear and transverse shear and axial loading. But the answer is not clear. But the answers that I got by different trial and error method ...
-1
votes
1answer
36 views

Why exactly do two parallel equal magnitude forces acting on a rigid body produce no rotational motion?

How exactly do we justify that two parallel forces $\vec{\mathbf{F}}_1$ and $\vec{\mathbf{F}}_{2}$ having the same magnitude, acting on a rigid body, do not produce a moment? Yes, if we consider any ...
-1
votes
2answers
39 views

Can we take rotational equilibrium of only one part of a body?

Can we take rotational equilibrium of only one part of a body? Such as in a step ladder, where BD is a rope. Can we take rotational equilibrium of AC about C, and not the full ladder?
0
votes
2answers
165 views

How does a balancing toy work?

I know that the balancing toys have their center of mass under the axis on which they are balancing. That's why they stay still. But when we give a little tap on it, it re-balance itself. But how does ...
16
votes
3answers
2k views

What holds up the lowest point of a rope following a catenary curve?

A catenary curve is the curve followed by a rope suspended at both ends in uniform gravity. I thought I would try to solve it myself because it seemed like a good challenge, but almost immediately I ...
0
votes
1answer
186 views

Why frictionless joints are assumed in pin-joint truss analysis?

In pin-jointed truss analysis, we consider some assumptions. One of them is that they have friction-less joints. Why do we have this assumption? What would happen if the joints were to have ...
1
vote
3answers
79 views

How is weight distributed in a stack of boxes? [duplicate]

Consider the following stacks of 2D boxes with uniform density: ...
0
votes
2answers
159 views

Why is the horizontal component of the reaction force at one of the hinges (which has a rounded bottom) neglected?

In the textbook "Engineering Mechanics: Statics (7th edition)" by James L. Meriam and‎ L. G. Kraige, Chapter 3: Equilibrium, in the section titled: "Examples of Free Body Diagrams", I found an example ...
1
vote
1answer
47 views

Is this system statically indeterminate?

In the static configuration of rectangular blocks shown below, we will assume that the gravitational force acting on each block is $1$. Each also has uniform density. We will also assume that: $(x_1,...
0
votes
3answers
49 views

Weight of objects

I recently observed that on a weighing machine(rectangular) a object weighed the same as the half portion of the same object with it's other half hanging out of the boundary of the machine (The ...
0
votes
1answer
204 views

Friction between ladder and wall (statics)

I was given the following task: My problem is the following: For $A$ and $B$ I’ve got friction forces $R_A$ and $R_B$. I can calculate those by using the formula: $R_A = N_A \cdot \mu $ $\mu $ is ...
0
votes
1answer
47 views

Force-couple system equivalence: 3 moment equations

In force-couple system equivalence, We can show that two systems are equivalent if the resultant force in both are equal and that it has the same line of action. So Rx1 = Rx2, Ry1= Ry2, Ma1 = Ma2 ...
1
vote
2answers
113 views

Static Equilibrium: Normal Force

Consider the following situation where an object (for example a person) is at rest at point D such that the system is in static equilibrium: Why is there no normal force present at point D? To my ...
1
vote
3answers
147 views

Equilibrium of a rigid body

Why is it necessary for a body to have the net torque acting on it be balanced along with the forces for it to be in equilibrium? Isn't torque just some special case of force like rotation is a ...
-1
votes
1answer
47 views

Statics: What it means if a rope snaps

There is a drawbridge that is held up by a hinge attached to a vertical wall on one side, and by a vertical rope on the other side. Say a horse starts walking from the wall towards the rope and at a ...
1
vote
1answer
122 views

Tension exerted by strings at corners of a rope grid [closed]

I am a software developer and helping someone with an art installation. It consists of a grid made of ropes. Grid is $12 \cdot 12$ meter and internal squares are $1 \cdot 1$ meter. Grid is suspended ...
1
vote
0answers
88 views

Express $\tan{\theta}$ in terms of $\alpha$ and $\mu_s$ [closed]

Problem: Determine the least angle $\theta$ where equilibrium is possible. Express $\tan{\theta}$ in terms of $\alpha$ and $\mu_s$ Attempt: I started of with drawing out all the acting forces: ...
2
votes
2answers
122 views

Conceptual Question about Suspension Bridge Forces

Two walkways are suspended from vertical rods. In the first scenario, one long rod supports both walkways and is attached to the ceiling. In the second scenario, two shorter rods are attached to each ...
1
vote
0answers
32 views

Conservation of percent difference?

I was doing a lab to experimentally determine coefficients of static friction between two surface. This was the basic set up: The mass of the block is a known quantity. I was checking the maximum ...
0
votes
0answers
38 views

How can this truss member be static?

I found this picture online of a truss and was wondering how the bottom right member can be static if its reaction at its rightmost joint is in the same direction as its reaction at its left joint.
-1
votes
1answer
124 views

Truss analysis how to calculate for a single beam?

Suppose I want to calculate the tension/compression force only in 4. Is there an easier way to calculate it or do I have to calculate everything with the joint method? I don't immediately see zero-...
2
votes
1answer
99 views

Why is shear stress equal to half of yield stress

Why is the value for acceptable shear stress equals to half of yield stress? $$ \tau = \frac{\sigma_{yield}}{2} $$ P.s Along the math behind it would be possible to explain this with visual consepts? ...
2
votes
0answers
142 views

Hard mechanics problem: Beam resting on three springs [closed]

I have trouble with following problem (ii): A uniform beam $AOB$, $O$ being the mid point of $AB$, mass M, rests on three identical vertical springs with stiffness constants $k_1$, $k_2$ and $...
1
vote
2answers
66 views

What friction vector direction will be in this case?

Two bodies 1 (at the top) and 2 (the rightmost one) with same masses are connected to each other with lightweight non-expandable thread thrown over sheave. The block A has an acceleration a. I need to ...
0
votes
0answers
32 views

How to calculate torque transmission forces?

I have been struggling with calculating forces that are driven by a single torque (motor). I can only calculate the force on the end of the driving stick. Please, can anyone guide me towards some ...
1
vote
1answer
37 views

Is there a quick way to convert between two coordinate systems?

I am solving a few Statics problems that ask to find the resultant moment that a given force produces about a given axis. The problem has two sets of coordinate systems (x, y, z) and (x1, y1, z) where ...
-1
votes
1answer
53 views

Reliable, intuitive method for working out the direction of static friction?

I've seen Consistent method for finding direction of static friction which was the closest question I could find, but I'd like something better. I need a method which : 1) Intuitively makes sense 2)...
0
votes
1answer
165 views

How to know what method to use when finding resultant forces?

I am quite confused as to what method should be used when finding resultant forces. Here are two examples of a question that asks to find the resultant force. One requires the parallelogram law to ...