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0

As far as I know, when a wheel rolls w/o slipping, it always has friction in the opposite direction of its movement. Here you go wrong . In pure rolling (that is no slipping ) the bottom point is at rest wrt ground . So there is no kinetic friction acting on it as there is no relative motion .But static friction acts . In your question gravity ...


0

Friction acts on objects at rest too . The definition meant that if there is relative motion between two objects then friction will act as a resistance between them . If you find two objects at rest even when an external force is applied on it then it means friction is acting on them . Had there been no friction there would have been relative motion and the ...


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Considering both the discs as the system , we can conserve angular momentum about their collinear axis of rotation . The torque due to friction will decrease the angular velocity of the disc having more angular momentum (before the collision ) while the torque will increase angular velocity of the one which had lesser initial angular momentum . I am assuming ...


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The resistance to motion can also occur when the object is at rest. I push on a book, and it doesn't yet move. The object is not in motion, so there must be force that balances my push. That force, which is resisting motion, is friction. When the two objects are in relative motion we call it kinetic friction. When they are at rest relative to one ...


1

Philosopher who said to you that the pressing force taken for friction's calculation is Normal force or reaction force exerted by earth on body? Actually, the pressing force is called the normal force (not reaction force) Since it is the force perpendicular or "normal" to the surfaces which affects the frictional resistance, this force is typically called ...


0

I think you just need to treat two forces separately relative to each body as $\vec{F}_1=-\vec{F}_2$ and $\lvert|\vec{F}_1\rvert|=\lvert|\vec{F}_2\rvert|$. Having in mind that $\vec{F}_1(t),\vec{F}_2(t)$ both are functions of time because the motion goes with constant acceleration.


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In the equation $F_f=\mu F_N$, where $F_f$ is the frictional force, $F_N$ is the normal force, and $\mu$ is the coefficient of friction, $\mu$ is sort of a way of expressing the quantity that you're looking for. You ask why this equation does not include an expression of the "roughness" of a surface, but it's not obvious to me how you would concisely ...


1

Even I didn't get you but I may help you how much I can by describing your case. Your case have two bodies which are being rubbed against each other in opposite direction with constant acceleration. The definition of friction is, "The resistance which either one of the bodies offers to this motion is called the force of friction and is said to be due to ...


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How the acceleration change may depends on the relation between the two bodies' mass and the coefficient of friction of the surfaces. I will assume the initial friction is exerted by ground. In the following I use U means upper body (your second body), L means lower (your first body), G means ground, 2 stands for 'to'(or any other prepositions). 1.If U is ...


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The force of friction will increase with the addition of the second mass. However, the mass of the system will increase as well, and the net effect is that the acceleration does not change. To see this, note that: $$a={F \over m}={\mu _kmg \over m}=\mu _kg$$ Where $\mu _k$ is the coefficient of kinetic friction between the moving body and the surface it's ...


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I'm afraid your separation of these two types of friction is not entirely useful in this situation. Rolling and sliding are, when you look very closely and over small time scales, just about the same. (The friction applied to a wheel, though, causes some rotation, which can lead to the wheel traveling over the surface). If I had to use your model of sliding ...


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Assuming the interpretation I suggested in the comments is correct. Consider the normal support force. It is an expression of the solidity of the surface that won't allow interpenetration. In order for penetration to not happen, there must be a force to prevent the supported object from accelerating toward the surface. Ultimately the origin of this ...


-1

why so complicated? Turning the steering wheel of a vehicle clockwise miraculously makes the vehicle rotate to the right. A clockwise rotating stone has its running surface on the right side more closely matching the speed of the pebble below it especially while decelerating than the left side which is sliding faster over the pebble. If the one foot diameter ...


3

but perhaps, given sufficient throwing speed If you throw your egg too fast, the force due air resistance $$F = \frac{cW\cdot A\cdot \rho\cdot v^2}{2}$$ will exceed the 50 Newton you mentioned before and the egg will break. and, or, car speed, perhaps it is possible If the car speed is fast enough the glass will of course break, since even ...


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For a viscous damper, the decay in the free oscillation amplitude is exponential (it is geometric for hysteric damping and linear for Coulomb damping). So if you have the time history of the amplitude of your decay and you know it is a viscous damper (which is the equation you gave) then you can measure the amplitude $A$ at two consecutive peaks and ...


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"Damping" in a system or model is the physical means by which energy can be dissipated. The model you cite, $F=-k_dv$, models by an approximation 'viscous' damping which is often used to model energy losses of surfaces sliding against one another - friction. In viscous damping the force opposes the direction of and is linearly proportional to the velocity. ...


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http://en.wikipedia.org/wiki/Static_electricity This is what I mean by static if their is a difference and I do think there is according to your reaction and your -1. Enlighten me. So confusion is out the way and I can ask the correct question. “We learn from failure, not from success!”


3

Your answer : The bowlers and fielders rub the ball to make the ball smooth and shiny on one side and leave it rough on the other side. To generate reverse swing. There is a lot of science behind swinging the ball. The ball gets reverse swing when it is quite old and you see not only the bowlers but the fielders as well rubbing the ball before every ...


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There are no simple "mixing" rules for defining pretty much any aspect of the physics of composite materials. Materials science is not that simple: chemical bonding of the same elements is radically different in different combinations. I think adding a new object to running code through the Factory Pattern for each and every new material you need is a ...


0

Static friction will always oppose the resulting force before friction is considered. If the downward force is larger than the upward one, friction will be upward. Else, if the upward force is larger, friction will point downward.


1

The direction of kinetic friction is in the opposite direction of the velocity of the box and independent from acceleration thus whether the $\mathbf a$ is positive, negative or zero does not affect the direction of the friction vector


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Gravity pulls in the center of gravity. It will be in the middle of both a cube and a ball in question. There will be a normal force on the cube on the ends. There will be a normal force on the ball at the contact point. If the weight pulls in the center further to the left (for a left directed incline) than where the normal force pushes, then the object ...


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Look at the forces -- and more specifically the torque. The sphere has the force of gravity pulling it downward, and the inclined plane pushing it out. The inclined plane exerts a force on the sphere at its contact point perpendicular to the plane. The force of gravity has some component along the plane, and some component perpendicular to the plane. The ...


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You'd have to check to see if the sum of the moments around the toe causes a rolling rotation about the toe. In the case of a cylinder, the toe is positioned in such a way that the moment about the toe always causes rolling. In general, draw up a free body diagram that shows all the forces and moments, focusing on the moments about the toe. Include gravity, ...


1

When we hit a friction-less surface with a hammer, we have to bring the hammer towards the surface with a velocity. Now it is given that we are bringing the hammer at a non-perpendicular plane. Therefore the velocity will have two components : perpendicular to the surface and parallel to the surface. The velocity parallel to the surface will remain ...


1

No. Lying down on a surface could only serve to change the coefficient of friction, but the problem asks you to suppose that it's zero. The general proof that you absolutely cannot do it by any motion, is the fact that with only gravity as an external force, momentum is conserved in the horizontal directions. The force of gravity and the normal force of ...



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