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votes
2answers
36 views

Static friction in a slope and two boxes problem

The context: Calculate the string tension in the situation where two boxes are stacked on a slope and moving with uniform velocity, given that the kinetic friction coefficient between the heavier (...
0
votes
1answer
28 views

Static equilibrium (possibility)

In static equilibrium for a ladder leaning against the wall it is supposed to rotate about a point. Why we are not assuming it to slide down as in our practical life?
0
votes
1answer
28 views

Friction Behavior at corners

The question: Find the range of value of $L/D$ such that the system remains in static equilibrium. And explain why such a range exists and not just a single value. This is the question where I ...
0
votes
0answers
55 views

Derivation of friction in interleaved phonebooks

Trying to understand the simple model in https://arxiv.org/abs/1508.03290, describing the friction between the pages of two interleaved phonebooks. Specifically I don't see how to get Eq. 1. Here's ...
-2
votes
1answer
602 views

Ladder and friction (wall and floor) [closed]

Here there is a problem and the proposed solution: UPDATE: I can't understand why getting the maximum friction to solve this kind of problem when it is known that static friction, depending on other ...
2
votes
1answer
49 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 ...
0
votes
1answer
39 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
1answer
428 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 ...
1
vote
0answers
36 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 ...
-1
votes
1answer
73 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
3answers
468 views

Static friction free body diagram on a flat plane

Do you include static friction on a free body diagram for a static box on a flat surface? Or do you just include Force of gravity and Normal force? We know when the box is moving there is Frictional ...
0
votes
2answers
168 views

What is the direction of friction in this example? Why?

I have difficulty knowing the direction of friction on static structures. The structure of the image is on equilibrium, and the exercise askes the maximum force P that the structure can take. Would ...
0
votes
3answers
105 views

Confused about direction of friction

Question : The system of two blocks and fixed pulley are joined by a cable as shown. Determine the mass $\textbf{M_2}$ required for static equilibrium. All wheels and pulleys have negligible friction: ...
1
vote
2answers
473 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 ...
0
votes
2answers
6k 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 "...
1
vote
1answer
508 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 ...
-1
votes
1answer
332 views

Equilibrium of rigid body [closed]

A uniform beam $AB$ of length $2l$ rests with end $A$ in contact with rough horizontal ground. A point $C$ on the beam rests against a smooth support. $AC$ is of length $\frac{3l}{2}$ with $C$ higher ...
0
votes
2answers
2k views

Minimum force needed to keep the book from slipping?

I would just like to know if my answer to part C is correct because I am confident in parts a and b, Also note that 51.5N is the wrong value for P. P=515N. Ok so since P= normal force, this means ...
1
vote
1answer
174 views

Interpreting force components in statics problems involving inclined planes or similar

I'm having troubles to understand how to interpret the components of forces on inclined plane in quite complicated situations. I will make an example of one of the cases where I get confused. ...
0
votes
1answer
70 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 ...
1
vote
1answer
3k 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 can ...
4
votes
4answers
12k 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 ...
0
votes
2answers
310 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 forces ...
-1
votes
1answer
515 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 ...
11
votes
2answers
2k views

Hydrostatic friction: why do water droplets stay at rest on an inclined glass surface?

This is a non-expert question on a (seemingly simple) text-book topic. The question is about "hydrostatic friction", defined as follows. Consider a drop of water resting on a flat surface. If the ...