-4
votes
0answers
28 views

Coefficient of Static friction [on hold]

Kindly provide the reasoning for the direction of friction chosen...
1
vote
3answers
74 views

Distinction between torque and force

Distinction between Torque and Force. Consider a case when a cylinder is rolling down a rough inclined plane. While analysing its motion, we consider the force applied by the friction and the ...
1
vote
1answer
20 views

Accelerated wedge [on hold]

Consider the following figure, where a mass $m$ is placed on a wedge which is accelerated to the right ($\vec a$) which could be negative. The coefficient of friction between the mass and the wedge ...
0
votes
1answer
17 views

Direction of friction force between two boxes

There are two boxes on top of each other. The bottom box is dragged right by a constant force. What is the direction of friction of the top box against the bottom box?
0
votes
0answers
29 views

Tension of two masses accelerating down an incline with friction? [on hold]

I have tried multiple times, and I can't seem to understand how to solve this question. The question goes as follows: Two masses, M and m accelerate down an incline. They are connected by a massless ...
0
votes
1answer
45 views

The forces acting on 2 boxes [closed]

Consider the following figure: The surface is not friction-less. When the force $F$ is applied on mass A: Is the force the mass A applies on mass B larger, smaller or equal then the Force that B ...
1
vote
0answers
39 views

How torque and friction cause wheel to roll

I apologize if this question has been answered before, but I did not find the explanation that I needed. If a torque is applied to a wheel situated on a frictional surface, what forces cause the ...
1
vote
0answers
97 views

Tension Problem: Solve for T for two sliding blocks connected by a string [closed]

The problem: Two blocks made of different materials connected together by a thin cord, slide down a plane ramp inclined at an angle θ to the horizontal as shown in the figure (block B is above ...
1
vote
1answer
56 views

Static and kinetic friction [closed]

Say you have block1 on top of block 2 and the whole system is accelerating toward the right at a certain acceleration. Due to inertia block 1 wants to move backward to the left so there has to be a ...
5
votes
2answers
123 views

Pulling apart two interleaved phone books

The TV show Mythbusters had an episode in which they interleaved two phone books and dramatized how hard it was to pull them apart. (A long time ago, a phone book was a book that had an index of phone ...
1
vote
1answer
23 views

Calculate coefficient of friction from deceleration with and without conservation of energy

How can I solve the following problem? A block that moves at the speed of 120 cm / s keep going for 70 cm before stopping. What's the coefficient of friction between block and table calculated ...
3
votes
1answer
87 views

Could $\int (\ddot\phi + \mu\dot\phi^2)d\phi$ ever be negative? How to show it?

I am working on the following problem: Given a mass $m$ at rest at the base of an incline surface shaped like 1/12th of a circle with radius $R$. The mass is pulled up the incline by a rope that ...
1
vote
1answer
30 views

Pseudoforce and friction: confusion

Consider the following situation. A block of mass $M$ is resting on a rough horizontal ground, and a frame is moving towards the right horizontally with an acceleration $a$. Suppose the coefficient of ...
0
votes
5answers
180 views

Who does work while walking?

While walking the work done by friction is zero. But who does the work, actually? How someone is getting displaced? This situation also arises when someone climbs without slipping or is climbing a ...
0
votes
2answers
49 views

Why is there a static frictional force on an object that rolls without slipping?

It is clear that if a frictional force must exist on an object that rolls without slipping, it must a static frictional force because the contact point of the object with the ground does not move. I ...
1
vote
2answers
43 views

Finding coefficient of friction between block and plane [closed]

An inclined plane makes angle $\theta$ with horizontal. Upper half plane is perfectly smooth where as lower half is rough. The block of mass m starts sliding from top. If the block again comes to rest ...
1
vote
1answer
46 views

Modeling a stool with three legs pushed on one leg

If a stool with three legs is pushed (horizontally) on one leg in the direction of the axis passing through the other two legs, it starts both moving and rotating. Is it correct to assume 1/3 of ...
1
vote
1answer
113 views

Moving wedge and pulley system

A wedge of mass $M$ rests on a rough horizontal surface with coefficient of static friction $\mu$. The face of the wedge is a smooth plane inclined at an angle $ \alpha$ to the horizontal. A mass ...
1
vote
0answers
30 views

Inclined plane problem with friction [closed]

A block of mass 6.0 kg slides from rest at a height of 2.0 m down to a horizontal surface where it passes over a 1.5 m rough patch. After crossing this patch it climbs up another incline which is at ...
1
vote
0answers
23 views

Static Friction on a Circular Road [duplicate]

I was recently brushing up on my dynamics, when I saw the interpretation of how a car moves in a circular road. Apparently, the car can stay in a circle due to static friction acting inwards. But I ...
3
votes
0answers
50 views

How to get rotation speed after disk-disk collision?

Assume two circular disks A and B collide. They have both initial linear momentum and angular momentum. If their surface has no friction, their angular velocity does not change after collision, so I ...
5
votes
5answers
470 views

Forces other than the fundamental interactions, e.g. friction

Forgive me for the silly question, but I just don't get it. I just completed an elementary course in mechanics, and I am curious to know what I am about to ask. We have, all year, dealt with many ...
8
votes
2answers
1k views

How much more efficient is a road bike than a mountain bike? [closed]

What would be a good estimate on the difference of efficiency between a road bike and a mountain bike? A number of links cite all the usual reasons: thinner tires, better aerodynamics... But I'm ...
2
votes
1answer
44 views

Lifting frictional force and relative values for kinetic vs static friction

My physics textbook says that friction mainly arises due to intermolecular attraction between atoms of the objects in contact and clashes between peaks are only significant for rough surfaces. I was ...
0
votes
2answers
42 views

Work done by a frictional force on a cylinder

A cylinder of mass $m$ and radius $R$, is rolled on surface with coefficient of kinetic friction $\mu_{k}$ about the axis passing through the center and parallel to the surface, with initial ...
0
votes
2answers
52 views

Can friction be brought in to zero value by means of laboratory experiments?

By newton's first law, an object will continue to be in the state of motion of rest until and unless an external force is acting on it. To prove or verify it experimentally today, is there any way out ...
1
vote
1answer
65 views

What force counteracts friction when a block is pulled?

Firstly, I understand and apologize that this is more of a physics question than a math question. I noticed that when I pulled a book out from under a pack of gum, the gum stayed largely in place (it ...
7
votes
3answers
964 views

What determines whether a pool ball will bouce backwards after colliding with another pool ball?

I'm no knowledgeable pool player, but I've noticed that sometimes when the cue ball hits another pool ball, they roll together; and sometimes the cue ball bounces back. And I have a very, very rough ...
0
votes
1answer
63 views

How to calculate energy to start movement?

So let me try to explain a little bit. Lets say I have a robot on wheels. I want this robot to push a block. Lets say the force to produce in order to move that block is 100N. How much energy will I ...
0
votes
1answer
37 views

Kinematics - moving body [duplicate]

If I have an inclined plane, which has acceleration $\alpha$, will a block placed on the inclined plane slip back with the same acceleration? (considering that the surface is frictionless)
0
votes
1answer
44 views

Does a Force on the block $M_1$ in this diagram have an effect on the block $M_2$?

Suppose we have two blocks: There is no friction. Does $F$ has the same effect on $M_2$?
0
votes
2answers
142 views

Why is the force of Friction less than the force applied on the block in this situation?

This is a seemingly basic mechanics problem but I'm having a dilemma in understanding what happens. You start with two blocks, one on top of the other (the bottom block has a larger mass than the top ...
2
votes
1answer
38 views

How does separation of tracks affect the acceleration of a rolling ball on the tracks?

If I have two metal rods arranged like a ramp with coefficient of friction $\mu$, at an angle $\theta$ to the ground, and a solid metal ball or radius $r$ and mass $m$ rolling down between the two ...
35
votes
6answers
5k views

How can the Earth keep spinning with a liquid core?

In regards to the 'conservation of angular momentum' being the explanation of why celestial objects spin... If you fill a ball or any other container with a liquid and try to spin it, you will not ...
0
votes
1answer
75 views

Force on a potentially rolling ball initially at rest

I'm a graduate student in mechatronics, but I give myself headaches on this astonishingly simple 2D problem. Imagine a ball (perfectly rigid) on an horizontal plane (perfectly rigid), initially at ...
1
vote
1answer
33 views

How to identify whether the friction is kinetic or static?

The body 'A' is moving forward with certain acceleration over the ground. The ground applies a kinetic friction force on 'A' in backward direction to oppose the relative motion. The block 'A' also ...
1
vote
1answer
46 views

Throwing ball against oily/slippery wall

I would like to know whether a ball bounces back normally if you throw it against an oily wall. Like a wall watered down with oil. Basically I want to know if it will actually slip before bouncing ...
1
vote
1answer
162 views

Block and Pulley Problem with Friction [closed]

1.) What is the acceleration of the hanging mass? (Indicate the direction with the sign of your answer.) 2.) Determine the tension in the cord. (Indicate the direction with the sign of your ...
1
vote
0answers
58 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 ...
1
vote
3answers
114 views

Why doesn't a block rotate due to friction?

In a horizontal surface, a block (cube) is sliding due to a sudden push. When the block slides, there is frictional force which is acting on the block. Frictional force will have a torque around ...
2
votes
4answers
81 views

Turning on a straight, unbanked, frictionless road

I was learning about circular motion when this question struck me: In real life situations we are able to take a turn along a circular arc with our bike because friction provides us the necessary ...
2
votes
3answers
239 views

Is friction a product of Newton's third law?

Newton's third law is defined as $F_{12} = -F_{21}$ Is friction a product of this law? For example, if I take my hand and slide it across the floor in the $+x$ direction... My hand exerts a force ...
1
vote
3answers
259 views

Why is using Newton's First Law failing me?

A factory worker pushes a 29.7kg crate a distance of 5.0m along a level floor at constant velocity by pushing downward at an angle of 32$^\circ$ below the horizontal. The coefficient of kinetic ...
5
votes
1answer
82 views

How can a reel of thread move in opposite direction?

There is a nice puzzle about reel of thread. I wonder why the solution works. The puzzle: You take a reel with threads on it. Inner radius r, outer radius R. You put it on a table. If you pull ...
0
votes
2answers
83 views

Is friction always constant?

Can the norm of the friction force change with time? Notice I said the norm which is in Newtons, can it change with time? Sorry if the question seems a bit confusing but I've done my best to explain. ...
1
vote
1answer
32 views

Clarification what exactly this question wants regarding force [closed]

I would like to ask you if the question asked What is the minimum force parallel to the plane, which can be prevent the block from slipping down the plane? I just did the calculation and and ...
2
votes
2answers
113 views

kinetic and potential energy

I have 2 cubes where one mass is greater than the other. $M$ and $m$, where $M>m$, and there is a hill that is symmetrical on both sides, and has a friction factor of $k$ between the object and the ...
0
votes
1answer
50 views

graphing velocity and time (v-t graph) [closed]

The question goes like this: If we push a body shortly uphill and it gets a starting velocity of $v \ ms^{-1}$,the coefficient of friction between the body and the surface is constant, represented by ...
3
votes
3answers
108 views

Time reversal symmetry in the presence of friction

I was reading a paper on time reversal symmetry, and came across an example of a pendulum swinging in the presence of friction: When we consider the more realistic physical situation of a swinging ...
0
votes
2answers
71 views

Physical interpretation of initial conditions for damped mass-spring system

I have background in pure mathematics so my question is about physical meaning. If we consider equation for damped mass-spring system, it is linear ordinary second order differential equation. So to ...