Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into static friction ("stiction") between non-moving surfaces, and kinetic friction between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities (see Figure 1).
Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other.Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces.Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body.
Internal friction is the force resisting motion between the elements making up a solid material while it undergoes deformation.When surfaces in contact move relative to each other, the friction between the two surfaces converts kinetic energy into thermal energy (that is, it converts work to heat). This property can have dramatic consequences, as illustrated by the use of friction created by rubbing pieces of wood together to start a fire. Kinetic energy is converted to thermal energy whenever motion with friction occurs, for example when a viscous fluid is stirred. Another important consequence of many types of friction can be wear, which may lead to performance degradation or damage to components. Friction is a component of the science of tribology.
Friction is desirable and important in supplying traction to facilitate motion on land. Most land vehicles rely on friction for acceleration, deceleration and changing direction. Sudden reductions in traction can cause loss of control and accidents.
Friction is not itself a fundamental force. Dry friction arises from a combination of inter-surface adhesion, surface roughness, surface deformation, and surface contamination. The complexity of these interactions makes the calculation of friction from first principles impractical and necessitates the use of empirical methods for analysis and the development of theory.
Friction is a non-conservative force – work done against friction is path dependent. In the presence of friction, some kinetic energy is always transformed to thermal energy, so mechanical energy is not conserved.
Hello all,
I need some help with a problem at statics, friction applied on threads. A threaded screw is given a ("horizontal") force of 100 N at the end of the handle. As the exercise states, they ask to calculate the force which occurs at the tube as well as the force needed to vise handle to...
I drew a free body diagram for the crate. I have normal force going up, weight down, static friction force to the left and the force of the crate sliding to the right. I'm assuming the truck is moving to the left.
I have Fnet=0 because the crate is not moving, so the forces are balanced. I...
Two boys are arguing over who gets to play with a toy. The toy has mass 3kg and is at rest on rough horizontal ground with coefficient of friction 0.3. The older boy pulls with a force of 26N at an angle of 39 degree above the horizontal. The younger boy pulls in the opposite direction with a...
This image represents the ramp.
The first part is pretty easy.
The red part has friction, and the ball rolls down it. The blue part has no friction, and the ball climbs it only owing to the translational kinetic energy that it gained at the bottom of the red ramp, which is only a fraction of...
It's the 10th question. Iam getting the ans for R=90cos34= 74.6 and F=-30.3N, so I get total contact force by using the formula c= sqroot(f^2+R^2)= 80.52N
The ans in the textbook is 92.2N. Iam not getting the right ans for coefficient of friction also which is 0.393
A toy car of mass 80g rolls from rest 80cm down a rough slope at an angle of 16 degree to the horizontal. When it hits a rubber barrier at the bottom of the slope it bounces back up the slope with its speed halved and reaches a height of 10 cm. Find the coefficient of friction between the car...
A book of mass 1.3 kg is on a plank of wood which is held at 16 degree to the horizontal. The coefficient of friction between the book and the plank is 0.45.
Find the size of the frictional force.
Iam getting the ans by using the formula F= coefficient of friction ×R
5.62N but the textbook ans...
A particle slides up a slope at angle 34 degree to the horizontal with coefficient of friction 0.4. It passes a point P on the way up the slope with 3m/s and passes it on the way down the slope with speed 2 m/s. Find the coefficient of friction between the particle and the slope.
Coefficient of...
A boy drags a sledge of mass 4kg from rest down a rough slope at an angle of 18 degree to the horizontal. He pulls it with a force of 8N for 3s by a rope that is angled at 10 degree above the parallel down the slope. After 3s the rope becomes detached from the sledge. The coefficient of...
A wooden block of mass 3.5kg is sliding up a rough slope and passes a point A with speed 20m/s. The slope is at 29 degree to the horizontal. The block comes to rest 25m up the slope. Find its speed as it passes point A on the way down.
I calculated coefficient of friction = 0.554.
U=20m/s v= 0...
A trolley of mass 5 kg is rolling up a rough slope, which is at an angle of 25 degree to the horizontal. The coefficient of friction between the trolley and the slope is 0.4. It passes a point A with speed 12m/s. Find its speed when it passes A on its way back down the slope.
So I did F=m×a...
Take rightwards as positive.
There are 2 equations of motion, depending on whether ##\frac {dx} {dt} ## is positive or not.
The 2 equations are:
##m\ddot x = -kx \pm \mu mg##
My questions about this system:
Is this SHM?
Possible method to solve for equation of motion:
- Solve the 2nd ODE...
A box of mass 50 kg is slowing down from 10 m/s on a rough horizontal ground. The coefficient of friction between the box and the ground is 0.3. To start with, the box is being slowed by a string providing a tension of 25N horizontally. Then the string breaks and the box comes to a halt under...
A snooker ball of mass 0.4kg is struck towards a cushion from 0.8m away with speed 3m/s. The surface of the snooker table has a coefficient of friction of 0.3. When the ball bounces from the cushion its speed is reduced by 20%. Find how far from the cushion it stops.
A bag of sand of mass 200kg is being winched up a slope of length 10m which is at an angle of 6 degree to the horizontal. The slope is rough and the coefficient of friction is 0.4. The winch provides a force of 1000N parallel to the slope. At the bottom of the slope the bag is moving at 2 m/s...
A gardener is pulling a wheelbarrow of mass 8kg from rest along rough horizontal ground. The coefficient of friction between the wheelbarrow and the ground is 0.6. The gardener provides a force of 50N at an angle of 30 degree above the horizontal as shown in the diagram.
a) Find the...
In a factory, a machine picks up a box by clamping it on both sides. The box of mass 4kg is held clamped on both sides by identical clamps with the contacts horizontal. The machine provides a contact force of 50N with each clamp. Find the minimum coefficient of friction between each clamp and...
A chair of mass 6kg is at rest on a rough horizontal floor with coefficient of friction 0.35. It is pulled horizontally by a force of 25N. A boy pushes down on the chair so that the chair is on the point of slipping but remains at rest. Find the force that the boy exerts on the chair.
A box of mass 20 kg is at rest on a rough horizontal ground. Find the magnitude of the total contact force in each of the cases.
a) The box is pulled horizontally to the right by a force of 40N
b) the box is pushed to the left by a force of 50N at 15 degree above the horizontal .
c) the box is...
Hi,
actually it's not my homework, I'm just practicing some academic problems after a long break but it seems that I should post this here anyway. Here's a scheme of the problem that I want to solve:
The task is to calculate minimum force ##P## for the system to stay in equilibrium.
And...
My understanding of static friction is that it is a resistive force in response to an applied force. I recently read the following example. A rope of uniform density, length L, is fastened to a plane with incline angle “theta” along its length. The question asks for the tension at the top of...
if the Work done by friction is -4.73 for object #1 but the work done by friction for object #2 is -4.63, in which scenario is the Work greater - the signs are throwing me off.
Also, let's say the initial elastic energy of a ball is 5 and its final energy is 0.27 (scenario #1) vs its final...
So I have questions on two separate questions. The first question is about the fbd of the plate attached to the pin. How can there be an Ax since there’s no other force in the horizontal direction wouldn’t the plate start moving on the x-direction due to imbalanced forces.
Second question about...
This was the answer key provided:
My questions are the following:
if the force required for rotational equilibrium is more than the limiting static friction, then the body will rotate aka slip over the surface. When it slips, the frictional force will be kinetic and not static, right?
If I...
In this part of the lab we pushed a block on a flat table and let it slide until it stopped. So it is decelerating with no force being applied to it while moving. In this case acceleration is negative. The only force acting on it is kinetic friction. Therefore I have come up with the following...
Hello Everyone,
I'm working on a future mechanical structure with a rotating shaft. In this project, I should be able to control the resistance on the shaft but instead of adding some extra weights on the shaft to increase inertia, I don't have any ideas. Does anyone have an idea of simple...
A 7.80 g bullet is initially moving at 500 m/s just before it penetrates a block of solid rubber to a depth of 4.50 cm.
(a)What is the magnitude of the average frictional force (in N) that is exerted on the bullet while it is moving through the block of solid rubber? Use work and energy...
I have no clue how to do this, so I did my best guess of it.
Friction is μN, N being the normal force.
The normal force when it is in contract with the pole should be V2/R, R being the radius of the pole.
So ΔT = μV2/R
The answer provided is μTΔθ
Hi,
We have a cylinder held by a rope . The rope holds it around its lower half.
If the center of mass of the cylinder is not in the middle, but towards a side, a distance "a". How does this offset affect to the friction on the rope?
or
How big does "a" have to be so the cylinder starts...
I have attempted this problem by solving for the normal force. (16.73)(9.8)-51.25(sin)(49.1). I tried to work that out but it was incorrect because apparently the vertical force is zero. Could I get an explanation on what that means and where I should start?
So first I made an equation representing the forces
Fnet=kx-12.8v
a=1/m(kx-12.8v).
Now I am not really sure how to get w from this. I could argue the mass is at its max amplitude when a=0, but that wouldn't help me find w. If I say x(t)=kx-12.8v, then 1/m would be w^2, but this isn't right...
Considering an stopped object in a horizontal plane, the frictional force between the object and the plane would be the product of the friction coefficient (static or kinetic if there was movement between the surfaces) by normal. Since the normal in this case would be given by N (vector) = - mg...
I have a question about friction between pulley and rope?
Does anyone know how to calculate friction between pulley and rope
I enclosed an example picture
Thank you!
As far as I’ve gathered, for a system to rotate there has to be some static friction acting upon it and dynamic friction can be zero. But now I’m a bit confused about this as we completely disregarded static friction in some tasks where a system was rotating. So was my original assumption wrong...
Hi,
I am working on a project regarding the friction drive on bicycles. I would like to design an assembly which has to be compact enough, and has to be able to produce torque that will move the bicycle from a stationary position, but as it turns out with my calculations torque required is...
Solution in 2ed manual:
Solution in 1ed manual:
Could someone explain why the work done by friction is multiplied by 2? I get that the distance traveled by the block in one cycle is greater than ##x_f+x_i##, but why is the coefficient two?
Summary:: I am not sure about how can I write an appropriate equation to a question which include friction force and initial velocity.
I came across a question that I am not sure how to write an equation.In the question, there is an object of mass m that is thrown into spring at v initial...
First calculated non conservative work from friction using Ff=umg. Non conservative work was -8.82.
Initial kinetic energy, 1/2mv^2, was 136.89.
Change in potential energy, 1/2k(x)^2, was 8.1216.
Ekf-Eki+Change Ep=Work NC
Ekf=W NC+Eki-change Ep
=-8.82+136.89-8.1216=119.9484
Ekf=1/2mv^2...
A force P is exerted on two articulated rods that are connected to two small blocks A and B. Both blocks have the same weight G. The magnitude of the force P = 1.26 G. The static friction coefficient between the blocks and the ground is 0.3. The mass of the rods may be neglected.
It can be...
Would we use the mass of the bucket and pucks to get a higher acceleration?
I don't understand the use of the pucks in this question?
How would the three laws relate to this?
Please scroll-down to Q50: https://www.undergraduate.study.cam.ac.uk/files/publications/engineering_s1_qp_2017.pdf
The correct answer is 'B', or 'mgsin(Θ)'. I put 'E', or 'μmgcos(Θ)'.
There are unofficial worked solutions which I have been referring to when I have attempted the question and...
re: https://www.physicsforums.com/threads/is-it-possible-to-solve-for-t.996132/post-6421205
https://www.physicsforums.com/threads/is-it-possible-to-solve-for-t.996132/post-6421230
Would it be possible to find t and r via the exact same equations as found in posts #4 and #10, and then find the...