# 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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### Tipping angle of a box [duplicate]

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!
15k 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. ...
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### 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?
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### 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 ...
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### 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) ...
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### 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 ...
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### 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 ...
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### 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)...
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### 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 $h\,\mathrm{cm}$ $\left(h > 2r\right).$ ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### If the output force to input force increases when we use a lever, what decreases? (mechanical advantage) [closed]

I'm stuck on this one, does anybody have any idea?
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### 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 ...
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### 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 ...
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### 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?
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### 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-balances itself. But how ...
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### 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 ...
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### 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 ...
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### How is weight distributed in a stack of boxes? [duplicate]

Consider the following stacks of 2D boxes with uniform density: ...
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### 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 andā L. G. Kraige, Chapter 3: Equilibrium, in the section titled: "Examples of Free Body Diagrams", I found an example ...
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### 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 ...
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### 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 ...
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### 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)...
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### 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 ...
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### Why don't underground tunnels collapse on themselves?

I understand that underground tunnels don't collapse because the forces acting on it must be in equilibrium but I don't know which forces are present and I don't know how they are built.
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### Best self-study books for static mechanics problems

Which book is the best for me to self-study/improve at static mechanics problems? I am looking for a book with a lot of ( only ) problems, not a theoretical book. Not only basic problems, the ideal ...
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### How does an Anti-tilt chair work?

These chairs are designed as per European Educational Standard Part 1 and 2. These are claimed by the manufacturer as Anti tilt, so basically it makes it relatively difficult for a child to fall when ...
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### Membrane shape under pressure

If I have a circular membrane that is fixed by the edges and then I apply a uniform pressure to the membrane (let's say the membrane is the top of a circular chamber that has a rigid wall and flat ...
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### Distribution of normal force on a book resting on the edge of a table

Assume a uniform book is resting on a table. The book has length $1$. But not the entire book is resting on the table, a bit $\alpha$ is sticking out of the table. Obviously, due to experience, we ...
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### Projection of force [closed]

So to find the projection along the cable in question 124 we used CA (not AC). Why? I thought that we always start from the end point of the Force, which is AC and not CA.
I have seen the following free-body diagram in an engineering paper, J. Compos. Constr. 9, 388 (2005) (e-print): As it is mentioned in the paper $f_j$ is the stress in the FRP layer (which acts ...