# Tag Info

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It's not easy pushing something with by hand with a constant force greater than kinetic friction. Try using a rubber band and a ruler to pull something across the table with a constant force. I think if you focus on keeping the rubber band stretched a constant amount while you pull you will notice the object will accelerate.

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I am aware that a constant force causes a constant acceleration but friction can counteract this. True. Although any non-zero net force acting on an object causes it to accelerate. The net force does not have to be constant in time for acceleration to happen. However, if I push something across a table, for example, it seems no matter how hard I push, ...

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There are several factors at play here: 1.The tread pattern of given slippers 2.The surface roughness (i.e, the unevenness of given given surface) 3.The coefficient of friction between surface and the slippers. To put in perspective it is obvious that more the coefficient of friction between surfaces, less the slipperiness. Unevenness of the surface ...

4

It doesn't matter whether the object itself is moving; what matters is whether the two surfaces involved are sliding past each other. If they are sliding past each other, the friction is kinetic; in contrast, if they are not, then the friction is static. When a wheel rolls without slipping/skidding, the part of the wheel that touches the ground does not ...

3

Hold a piece of wood against a sanding belt. In your frame, the block is not moving, but kinetic friction is exerting a force: you have to hold the block still energy is transferred: the block gets hot, and pieces are pulled off it

3

The groove applies a normal reaction on the block, which is the reason that the block rotates along with the table with the same angular velocity as the table. Now since this normal force is tangential to the table it causes the tangential speed of the block to increase. Tangential velocity is equal to angular velocity cross radius and angular velocity ...

3

I don't know if you've learned about energy and power yet, but if you have, that leads to a pretty plausible explanation. As you push this object with force $F$ at speed $v$, the power you expend (like the horsepower of a car) is given by $P=Fv$. As you start the object in motion, it's accelerating. But this process of acceleration is limited by the power ...

3

The maximum force that friction can apply is given by the equation $F = μ N$. Here, $N$ is the normal force, which on a flat rigid surface is equal in magnitude to the weight of an object. The coefficient of friction is $μ$, which is related to how much "grip" the surface has - how rough or smooth it is. Ice has a low coefficient of friction, while sandpaper ...

2

I actually think this is kind of a great question, but I'd like to focus on one of your statements in particular: "The object seems to always travel at the same velocity as my hand, does this mean I am not actually applying a constant force?" If you are pushing an object, this will be true regardless of the force you apply. That's part of the definition of ...

2

The thing confusing me is which direction will be the force $ma$ acting on the body? If the body is at rest with respect to the incline, then it must be only moving (accelerating) horizontally. By Newton's second law, this means that the net force acting on the object is horizontal to the right with no vertical component. Some force should be acting on ...

2

The friction force opposes the direction of the movement, not necessarily the weight's parallel component. If the tension force is greater than the weight's parallel force the object will want to slide up the ramp and the friction force will be pointing opposite of the tension force along the ramp. The static friction force will try to hold the object ...

2

You are not pushing the object with the constant force. It's not a question of physics but the one of biology. Your brain does not command your muscles to apply the constant force, it commands to move the body part to arrive at a certain position or move at a certain speed by applying whatever force is necessary. The only exception would be applying ...

2

The friction just provides the grip. The torque of the engine does the work. Its the same when you start running- your legs exert the force and friction just prevents your feet slipping backwards.

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Yes work done by kinetic friction may be zero for example:- consider a block slipping on ground work done by kinetic friction will be negative in ground frame but now observe the block w.r.t block itself now work done by each and every force will be zero as displacement of block w.r.t itself is zero.

1

I can't really answer this. But I think the concrete road will have more sharp edges that make tiny cuts in the tires, and the tar will be a little bit sticky and pull at them in multiple directions. The tar might tend to slightly dissolve in the tire and vice versa. Would that make the tire wear faster or slower? It would surely reduce miles-per-gallon, ...

1

It has to do with this: In a perfect world, turns would all be banked so you could traverse each at full speed and not skid sideways off the road. Since it is not always possible to bank the roadway surface at the right angle to support a full-speed turn, the reduced speed limit in a turn is set to accommodate the existing bank angle and turn radius minus a ...

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As outlined by OP in a comment, we are dealing with an object lying on a surface with one side fully in contact with that surface. Kinetic friction doesn't depend on area. In only depends on normal force (the pressure on the surface):* $$f_k=\mu_k n$$ $\mu_k$ is the friction coefficient and can be thought of as a constant (depends on the two materials, on ...

1

If the groove is sufficiently deep/steep-sided to retain it, and assuming the body starts off somewhere in the groove that is not at the exact centre of rotation, then the body will slide to the end of the groove. That will happen because the wall of the groove will press against the body and accelerate it and there is no centripetal frictional force to make ...

1

The thing confusing me is which direction will be the force ma acting on the body? There are only two forces on the mass. There is gravity, and there is the normal force from the ramp. The sum of those forces will generate a resultant acceleration. Some force should be acting on the plane giving it acceleration a then at the same time body will also ...

1

You are basically describing a solenoid engine, these are quite functional, and could probably be made large enough to propel a full sized car. Although not a very energy efficient, or smooth operating design for an electric motor. Here is a video link to a small 4 solenoid engine: https://www.youtube.com/watch?v=x4im3M9IFcI If you type in "solenoid engine" ...

1

For a frictional force (i.e. one that slows down the particle), $b$ must be negative. When you set $b<0$, you obtain: $$x(t)=\frac{i|b|^{1/2}}{(mv_0)^{1/2}}\tan\left(\frac{(mv_0)^{3/2}}{i|b|^{1/2}}t\right)=\frac{|b|^{1/2}}{(mv_0)^{1/2}}\tanh\left(\frac{(mv_0)^{3/2}}{|b|^{1/2}}t\right)$$ since $\tan\left(\frac{k}{i}t\right)=\frac{1}{i}\tanh(kt)$. This ...

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It is the static friction between the bottom of the tire and the road surface that keeps the tire from slipping or skidding (kinetic friction). Even though the tire is rotating, the bottom of a non slipping tire is in static contact with the road. When applied force is greater than static friction the wheel will slip. This can be caused by hard braking (...

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Let us look at the problem of terminal velocity When an object which is falling under the influence of gravity or subject to some other constant driving force is subject to a resistance or drag force which increases with velocity, it will ultimately reach a maximum velocity where the drag force equals the driving force. This final, constant velocity of ...

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[...] it seems to allow relative motion between the ground and the car. While there is relative motion between car and ground, there is not relative motion between wheel and ground. And that's what matters, because that's where the friction is. Think of walking. Your body moves relative to the ground. But at each step, your foot on the ground is stationary....

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