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.
Homework Statement
Homework EquationsThe Attempt at a Solution
I had someone help me with this problem (not on here) and their process and units don't seem to match to me. Or is this correct?
Homework Statement
At the instant shown, the driver of the truck has just pressed the accelerator pedal down and the truck has suddenly acquired a tangential acceleration of 2.2m/s^2.
Coefficient of static friction between crate and tray = 0.4
Coefficient of kinetic friction between crate and...
I am having my students do a lab to calculate the coefficient of static friction along a ramp. They are calculating the coefficient of static friction between felt and the table to be something like 0.40, yet when i did this lab, but along a horizontal surface, and not with a ramp, i get a...
Hello all.
I have a doubt about the work done by friction force on a wheels , in two diferent situations:
a) In Morin's mechanics book, chapter 5 (page 146) he considers the situation in which a car is braking without skidding. He claims that the friction from the ground on the tires causes...
Homework Statement
A block is held between two walls. One static, one applying a force. If the block weighs 5kg, and the coefficient of static friction between each wall and the block is 0.4, what horizontal force is required by the wall applying it?
Do both walls contribute an equal vertical...
For my final year project at uni, I am designing a new racquet grip. Past of investigating current products, I am going to test the friction properties of current grips. My plan is to rub a number of grips for a set time and then, using a heat sensor gun, measure the grips heat.
My question...
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A 3.0 kg block is held against a spring with a force constant of 125 N/m. The spring is compressed by 12 cm. The ice is released across a horizontal plank with a coefficient of friction of 0.1
A) Calculate the velocity of the block just as it leaves the spring. Assume the...
Consider a object of 5 kilos which is fixed with 4 rolling tyres (like in a trolly) which is in a slanting position of 30 degree angle.
My question:How to find the force required to move the object upwards the slope along with rolling resistance considered?
I tried the force using the F push...
This is not a specific problem. It pertains to all the problems I'm working on and only requires that I have one concept explained.
If an object is being pulled up a plane by a force parallel to the plane, does the friction work against the parallel component of the gravity or the force pulling...
Homework Statement
Find the minimum mass that is needed to get the system moving and the acceleration of the system once it starts to move. The coefficient of static friction between the mass and the table is 0.54 and the kinetic friction coefficient is 0.3.
Homework Equations...
Homework Statement
This is my problem in all its glory.
Homework Equations
f = uN
The Attempt at a Solution
For part a I simply did that tan(alpha) = f/N and therefore alpha = arctan(f/N).
This simplifies to alpha = arctan(u). I believe this part is correct.
The second part of this question...
Homework Statement
At a construction site, a 62.0 kg bucket of concrete hangs from a light (but strong) cable that passes over a light friction-free pulley and is connected to an 80.0 kgbox on a horizontal roof (see the figure (Figure 1) ). The cable pulls horizontally on the box, and a 50.0 kg...
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Two blocs with the same mass have the same rope which links them. The friction coefficients are the same whatever the surface. The blocs are initialy stationary and we let them move. What is the module of the acceleration of the blocs if static coefficient of friction =0,25...
I have an Atwood Machine. I have an aluminium Pulley of radius 4 inch. A gym cable running over it. Not sure coefficient of friction but smooth movement. One end of rope, I attach wt. of 0.5 kg. I had to attach weight of 1 kg for acceleration to start. If I attach 2 kg, I had to attach 3.1 kg...
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Two blocks are arranged at the ends of a massless string as shown in the figure. The system starts from rest. When the 2.33 kg mass has fallen through 0.315 m, its downward speed is 1.31 m/s.
The acceleration of gravity is 9.8 m/s^2.
What is the frictional force between...
Can someone please explain me the direction of static friction? I know kinetic friction is always going against the motion of an object but for static friction it depends.
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The mass of a car that acts on one wheel is 100 kg. The elasticity (spring) constant in the suspension system of that wheel is k = 10^4N/m. Design the strut (find the friction/resistance constant c) such that any vertical motion of the wheel (set up for example by going over...
Homework Statement
An ice-fishing hut weighing 52N sits on dry, frozen lake.
(a). What is the magnitude of the initial horizontal force required to make the ice-fishing hut start sliding across the surface of the frozen pond?
(b). Once the ice-fishing hut has begun sliding, what force is...
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Two trunks sit side by side on the floor. The larger trunk (52kg) is to the left of the smaller trunk (34 kg). A person pushes on the larger trunk horizontally toward the right. The coefficient of static friction between the trunks and floor is 0.35. Calculate the force the...
Homework Statement
in the question you're having to solve for this.
A force is applied at a angle of 30 degrees on a object that weighs 12kg that is also moving at a constant velocity. kinetic friction is equal to .70
i am confused on how to find the Force applied to achieve a constant...
Homework Statement
An electric motor is used to pull a 125 kg box across a floor using a long cable. The tension in the cable is 350N and the box accelerates at 1.2m/s2 (forward) for 5.0s. The cable breaks and the box slows down and stops. Calculating the coefficient of kinetic force?
Given...
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Calculate how much force you would have to apply to the crate to get it to go at constant speed up a 30 degree ramp.
Homework Equations
Using kinetic friction for equation.
The Attempt at a Solution
I couldn't find the formula for kinetic friction which also includes...
Homework Statement
We are dealing with a block on an incline that you can alter the angle with.
The inclination angle was increased until we reached a certain angle(critical angle) that the block just begins to slide at. Use this critical angle and your previous answers for the normal force...
can kinetic friction cause a torque? (can it result in rotation)
Or is it that only static friction can cause a torque?
Can static friction do work on a rolling object?
I think it can? because the rotational kinetic energy is increasing? is this right?
HELP!
Homework Statement
A .5 kg block of cheese sits on a level table. The coefficient of static friction is .60. Three strings are tied together in a knot at a point, K. One string is tied to the cheese, the other on a wall at a 30 degree angle, and in the middle of those two strings a mouse hangs...
Homework Statement
This isn't a problem from a textbook or homework but just a general question.
Say there's a car traveling in a circle and that the track has some coefficient of kinetic friction µ. What would make the car skid?
Homework EquationsThe Attempt at a Solution
I'm thinking that...
When a car moves forward, the wheel turns it exerts a force on the road in the opposite direction of travel, and friction counter acts it. the wheel turns and the car moves forward This implies that friction on the wheel is acting in the direction of the car moving. Though I thought that...
Hello! I just need someone to check my work here. I already turned in the homework with my hunch, but now I just want to check my work because it is killing me not knowing 100% :) I am having strong conflicting thoughts on particular parts and thought I'd post it here for clarification. I will...
Hi,
If I have a ball at the top of a ramp, it will have rotational and translational kinetic energy as it begins moving. If the ramp was frictionless, just to confirm, would it be possible for the ball to rotate or would it just slide with the point of contact on the ramp fixed?
Also, if there...
I apologize in advance for not exactly adhering to the template, but the question I have here arose from my attempts to solve the following exercises, so please bear with me. (Edit: I also apologize if discussion of a concept belongs in a different forum, as this is not exactly a homework...
Homework Statement
A block is projected up a 30° slope at 4m/s. When it is moving the coefficient of friction is 0.3. When the block is stationary the maximum coefficient of friction is 0.5.
a. Calculate how far up the block will go.
b. Show that the block will not remain there.
c. Calculate...
Homework Statement
What is the minimum coefficient of friction needed between the tires and the ground so you make the turn safely?[/B]
Car= 1394.7kg
You=75kg
Radius of turn = 40m
Velocity = 20m/s
Homework Equations
Fnet = MAc (Ac = centripetal Acceleration) = Force of friction
Force of...
Homework Statement
A 1000N crate is being pushes across a level floor at a constant speed by a force (F) of 300N at an angle of 20 degrees below the horizontal, what is the coefficient of kinetic force?
Homework Equations
Fk= uk*N
uk= Fk/N[/B]
Fk=F2
The Attempt at a Solution
in the back of...
Homework Statement
A student could either push or pull, at an angle of 30 degrees from the horizontal, a 40kg crate, where the coefficient of kinetic friction is .21. The crate is moved 18m. Calculate the minimum work for pushing and pulling.
Homework Equations
W=F•(change in)X•cos(angle in...
Homework Statement
A horizontal force of 150 N is used to push a 50.0 kg packing crate a distance of 5.00 m on a rough horizontal surface.
The acceleration of gravity is 9.81 m/s2 .
If the crate moves with constant velocity, calculate:
a) the work done by the force. Answer in units of J.
b)...
According to Newton's 3rd law, for every force there's an equal opposing force. Since a block is sitting on an inclined plane, wouldn't that mean the static friction is acting like the opposing force for mgsinθ thus, mgsinθ=static frictional force? Please respond
Hi guys,
I trying to understand one thing that I don't know where came from. To visualize the problem I will used the drawings from book.
The question is for direction of Force Fb on drawing (b) and (a). I was always learned that friction is acting on direct opposite to motion. In drawing...
Homework Statement
A lab I've performed was measured using forces. As the mass increases, the force does as well. The inclined plane is at an angle of 30 degrees. Now, finding the coefficient, should the kinetic and static friction be decreasing on a plane? I've measured the frictions on a flat...
Homework Statement
James bond is standing on a large frozen lake and fires his handgun horizontally. This exerts 1400N of force on the bullet over a distance of 10cm before leaving the barrel at 200m/s. What is the coefficient of kinetic friction between bond and the ice if he slid for 24.2 s...
Homework Statement
A car moving at 50mph coasts to a stop while traveling a distance of 150ft on level ground. what is the size of the friction force needed to bring this car to rest?
Homework Equations
vf^2 = vo^2 + 2a(xf-xo)
F=ma
Fk=un[/B]
The Attempt at a Solution
I first converted...
A tractor pulls a 5000kg asked up a hill at a constant velocity. If the hill had a constant grade of 30° with respect to the horizontal and there is a 10,000 N frictional force between the sled and the ground, what is the minimum force the tractor must exert on the sled?
I think I'm supposed...
Homework Statement
Two discs of different radii and masses are kept on a smooth horizontal table and both are free to rotate about their fixed central vertical axis. One of them is given some angular velocity while other is stationary. The rims are brought in contact. There is friction between...
I am trying to solve a homework problem that involves Work and friction but don't understand why if a force pulling upward on the object, the normal force becomes N = mg - Fsin(o)
shouldn't it be N = mg + Fsin(o) since both forces are acting upwards? (the normal force and the force applied)
Homework Statement
A block of mass m rests on a horizontal table. The block is pulled by a massless rope with a force F at an angle θ. The coefficient of static friction is 0.60. The minimum value of the force needed to move the block depends on the angle θ
a)Discuss qualitatively how you would...
I have been teaching Physics at the introductory level now for over 30 years. In that time I have taught a lot of labs on friction. Using the small masses readily available in the lab and using motion detectors to measure the velocity of the objects neither I nor any of my students has ever...
Hi,
I'm wondering what's going on when a friction force of a surface is applied to a moving block as the block slows down to zero and it, the friction force, is the only horizontal force applied. Does the friction force continue at a constant value until the last moment and just drop to 0N or...
Homework Statement
Homework Equations
Fnet=m(v^2/R)[/B]The Attempt at a Solution
I understood the FBD and how to find the bank angle. I just don't fully understand what part a and b are giving me in terms of friction. So for a, since it is skidding would only kinetic friction be used? Then...