The resistance a surface or object encounters when moving over another.

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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 ...
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4k views

How does static friction increase with increase in the applied force?

My book says that 'Between surface of contact between two bodies there are contact forces applied between each other (they are equal in magnitude but opposite in direction,obeying Newton's 3rd law) ...
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1k views

How does rolling resistance of rail wheel depend on diameter?

Freight train is more efficient than truck due to lower rolling resistance. And I wonder which one has lower rolling resistance<>, small diameter or larger one or it doesn't not depend on diameter ...
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Is water considered a substance with low friction or high friction?

Like, for example, rubber is a substance with high friction, as an object with neither high or low friction would easily stop on it, and wouldn't skid. Ice is considered an object with low friction, ...
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63 views

An object is accelerating on a rough surface with frictional force of 10N. Is the friction doing any work on the object?

This question might look stupid to some but I am in great confusion. An object, say a box, is moving on a surface with some velocity v and is accelerating. It means that the force applied by the box ...
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58 views

Why does an ice hockey stick, when thrown on ice always rotate and translate together before coming to rest? Why not only rotate or only translate?

When a hockey stick is thrown on ice it simultaneously rotates and translates before stopping. Friction probably plays the main role here, along with the shape of the stick. I think maybe it is due to ...
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142 views

Why do objects move when you apply a force that's equal in magnitude to the friction? [duplicate]

If the friction on an object is 200 N and you apply 200 N, it seems, the forces should immediately cancel each other out since the friction and your applied force go in opposite directions, leaving ...
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2answers
285 views

Which of these two forces is stronger: static friction or kinetic friction? [duplicate]

Which of these two forces is stronger: The force of static friction or the force of kinetic friction? I am having a hard time understanding this concept of friction, so please explain your answer!
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1answer
137 views

When will the pringles can fall?

When I'm pushing a tall, cylindrical object stood on its end (like a Pringles can) I can push it near its bottom, and it will slide forwards, or push it near the top, and it will topple over. So, ...
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98 views

Theoretical Question about a Frictionless Rope

This is kind of ridiculous to imagine, but say a person could somehow tie a frictionless rope into a knot. After making the loop and everything, and tightening the knot, technically the knot would ...
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257 views

Confusions in the 'Adhesion Theory of friction.'

While reading about the Adhesion theory of friction on this site, I came to some points which I couldn't understand. I have highlighted them: ...Adhesion approach is based on the partial ...
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326 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 ...
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3answers
652 views

Why friction is zero when wheel slip is zero? [duplicate]

From most graph, when the tire doesn't slip, then the friction is zero, for example see the below image Why there is no friction when there is no slip? As the car stand still on slope, there is no ...
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5k views

Direction of force of friction?

I know that friction opposes the direction of the velocity, but the problem is when I don't know what the direction of the velocity is. When I'm drawing a FBD for complex systems with ramps and ...
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3answers
813 views

What stops the car?

Centre of mass of a system cannot change its state of motion, unless there is an external force acting on it. Yet the internal force of brakes can bring a car to rest. Then what stops the car?
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1answer
745 views

What is the friction between cylinder and wall (ground)?

A hollow cylinder (radius $R$) is rolling against the wall at angular speed $\omega$. The coefficient of friction between the cylinder and the wall(ground) is $\mu$. After how many rotations the ...
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5k views

Is it possible to find out the distance traveled by a car if the force applied on it is given?

Say you have car which produces $F$ amount of force which is transferred to the wheels directly. Now assuming that there is air friction which is causing a retarding force proportional to the ...
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1answer
1k views

What forces act on a person sitting in a chair with wheels when they push off another stationary object

What is slowing me down when I push off my desk? What are the "Major" contributors? and Does how hard I push with one hand (or with two hands) make a significant difference?
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Terminal Velocity

Let Suppose a bullet of 2 gram is falling with the speed of 200km/h. Now how can we know the time after which it gains it terminal velocity. Also when it gain its terminal velocity the force of ...
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1answer
73 views

Understanding Newton's Laws of Motion

I'm having difficulty understand Newton's laws of motion in practice, and how to model true dynamic systems. There are two examples below, where I cannot quite figure out what the true forces and ...
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1answer
57 views

How I think about rolling [closed]

Below, I have written how I think about rolling. I wish to know if my idea as to how it works is correct. Consider a rigid ball on a plane which has considerable friction. If you push the ball ...
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2answers
39 views

Dynamical friction force

Let we have a ladder leaning on the wall. Initially we hold the ladder and as soon as we release it the ladder starts to slide. My question: during the slide, are the friction forces at both ends ...
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2answers
163 views

Free body diagram for two masses on inclined plane with frictions

I'm a bit confused about free body diagrams on inclined planes with frictions. Consider the situation in the picture, where $A$ and $B$ slide togheter on a inclined plane and I want to find a force (...
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1answer
62 views

Rotational equilibrium Paradox

A block of mass M and height h is moving on a rough surface of coifficent of friction 0.5 .The block is moving with a velocity v at some instant. if we balance the torque due to frictional force and ...
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340 views

How does this spool have an angular acceleration opposite to its acceleration?

Consider this spool. It rests on a rough horizontal force. The green lines are the ground, and a line parallel to the ground. The spool is pulled without sliding by the thread (with tension T), with ...
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3answers
51 views

The formula for the kinetic friction on inclined surface

I'm confused about the formula for the force of friction on inclined surface. It says that $f$ (force of friction) = $\mu N$ (where $\mu$ is the coefficient of the friction). Is: $$f = mg\cos(a)\...
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150 views

Frictional forces apposing motion

Please could someone help with some physics about resistive forces that would slow a ball down which is rolling across a floor. I have found conflicting bits of information about the effect friction ...
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258 views

Work done by friction on car

David Morin, in "Introduction to Classical Mechanics" says that friction does not exert a force on a car because the ground is fixed but that KE of the car is changing to internal kinetic energy in ...
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497 views

Can there be friction unless the objects in contact are not acted upon by an external force?

The definition of friction I read from The book, General Physics written by Henry Crew is that, The resistance which either one of the body offers to the motion is called force of friction". If it is ...
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179 views

If the force of friction is 20 N for a moving body does acceleration increase with the increase of the mass?

A body is moving and the only force acting on it is the force of friction. If we put another body on this moving body somehow the force of friction will increase; does its acceleration change?
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791 views

Can a thrown egg chip (or break) a car windshield?

Is it possible to throw an egg with such speed that a car windshield will chip (just like with stone chips?) I have searched around for existing research in the area and have found that the impact ...
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912 views

Inclined pulley with unknown hanging mass: when won't the system accelerate?

We have an inclined pulley with angle of $30° $ a block with mass of $10 kg$ placed upon it and It is attached by a rope over a pulley to a mass of $M_A$ which hangs vertically. If $μ_s=0.4$ and $μ_k=...
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1answer
453 views

What forces cause the centripetal acceleration in circular motion on a merry-go-round?

Suppose you stand on a merry-go-round spinning at $f$ revolutions per second and you are $R$ meters from the center. What forces act on you? If you were tied to a rope like in Fig 2 you would follow ...
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76 views

Why is it that friction apparently decreases with speed? [duplicate]

Whilst thinking of a trick where a magician pulls a tablecloth directly from under a full set dinner (a classic) I wondered why friction doesn't increase as speed does. I get that they use a pretty ...
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246 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 ...
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505 views

Why does a car bonnet (hood) rise when you connect the clutch with a brake on?

Is the rotational force to overcome the brakes moved to the opposite effect of moving the car chassis, until the brake is released?
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238 views

Energy of a damped oscillator

$$ E=\frac{1}{2}m\left(\frac{dx}{dt}\right)^2+\frac{1}{2}m\omega_0^2x^2. $$ This is the equation for the energy of a oscillator. The second term is the potential energy. Now, my question is, will ...
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116 views

Shaking water inside bowl causes waves but why does the water stabilize?

Suppose you shake water inside a container, then at first the waves goes up and down strongly but they gradually dissipate. What makes them dissipate?
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717 views

Does anti-lock braking system (ABS) perform reverse rotation sometimes?

In cartoons we can see, how vehicles brake by rotating wheels reverse. Will this be helpful sometimes in real situations? I know that the main tactics of ABS is to maintain tractive contact. But may ...
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$\gamma$ in Newton's Second Law of Motion in Differential Form

I am teaching myself Differential Equations from a website. In the website I am up to Direction Fields and an example of a differential equation is Newton's Second Law of Motion. It is written on the ...
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1answer
987 views

Friction force and contact area [duplicate]

It's usually stated that the friction force is independent of the area of contact (Amontons' Second Law). I've always thought that this shouldn't be true, because the atraction between molecules ...
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Physics behind Water drops during falling from a tap

what is physics behind Water drops during falling from a tap. water drop animation A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces. Why Water ...
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1answer
207 views

Is energy “destroyed” when walking?

Conservation of energy states energy can't be destroyed, but isn't energy used up when walking in a straight line? If your not walking up a slope, kinetic energy isn't converted to gravitational ...
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85 views

Horizontal rolling without slipping

I'm trying to find the friction coefficient that makes the body roll without slipping but I just can't reach a value. The force is applied on a small central disk of radius $r=0,03\, m$ and mass $m=0,...
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63 views

How is frictional force dependent on normal reaction?

It is a general concept that horizontal forces can only influence physical quantities along horizontal direction; similarly vertical force can produce acceleration etc. only along vertical direction. ...
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The instability of dry friction

Based on Newton Dynamics, the kinetic force of friction of any moving object can be found by using formula, $$F_f = \mu_k F_N $$ This means that if $\mu_k$ and $\ F_N$ remains constant, the ...
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73 views

What Feynman meant in description of reversible machine and levers

In chapter four of the part one of the lectures, he mentions: (..) A machine that we actually use can be, in a sense, almost reversible: that is, if it will lift the weight of three by lowering ...
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77 views

How does friction affect the motion of a pendulum?

I would like to know what is the difference in the equation of motion of a pendulum in the presence or the absence of frictional forces. And how this translates to the solution of those equations?
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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. ...
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66 views

Work done by a friction in rolling

When force is applied on extended objects at some point, the work done by this force on this object $\vec{F} \cdot \vec{dr_{P}}$ where $P$ is the point of application of force. When the object is ...