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
A man of mass ##80## kg, stands. on a horizontal weighing machine, of negligible mass, attached to a massless platform P that slides down a ##37^{\circ}## incline. The weighing machine reads ##72## kg. Man is always at rest w.r.t weighing machine.
Calculate:
(a) The...
Homework Statement
The brick mass 500g is pushed on hill with velocity 200 cm/s, how far can the brick reach before it stops when μ=0.150
Homework Equations
W=Fdcosθ
E=1/2mvv
The Attempt at a Solution
I got about 1 m before the brick stops, does it correct?
Homework Statement
Find the mass of the object which is being pulled by 40 hp engine with a constant speed 15 m/s (μ = 0.15)
Homework Equations
P=Fv
F=μN
The Attempt at a Solution
I got about 1,350 Kg for the answer but I don't know why P=Fv( It is just included in the problem )
First, I...
Homework Statement
A 500 g block lies on a horizontal tabletop. The coefficient of kinetic friction between the block and the surface is 0.25. The block is connected by a massless string to the second block with a mass of 300 g. The string passes over a light frictionless pulley. The system is...
Homework Statement
"When the three blocks in Fig. 6-29 are released from rest, they accelerate with a magnitude of ##0.500 \frac{m}{s^2}##. Block 1 has mass M, Block 2 has mass 2M, and Block 3 has mass 3M. What is the coefficient of static friction between Block 2 and the table?"
Homework...
Homework Statement
I think I am lacking some concept. I can't solve this one:
There are three blocks of masses 2kg, 3kg and 7kg lying on a frictionless table with the 7kg block on bottom 3kg in the middle and 2kg on the top. A horizontal force of 10N is applied on the bottom block. The...
Homework Statement
Three blocks A, B, and C of masses m1, m2 and m3 respectively are lying on top of each other on a frictionless table with A on top and C on bottom. The coefficient of friction between A and B is u1 and between B and C in u2. Find the accelerations a1, a2 and a3 of the three...
What does the line in the rectangle box means? (What is the difference between limiting friction and centripetal frictional force?)
What type of motion is meant by skidding?
http://prnt.sc/c7ptm8
Suppose two rigid circular coins are lying on top of each other. A horizontal force on the top coin is applied. So, I think there are two possible scenarios:
1. Both move together with common acceleration (if friction between them is strong)
2. Only the top coin slips over the bottom (if...
As far as I know both the friction or the frictionless contact types in Ansys doesn't prevent motion in the perpendicular direction. I have been following this tutorial https://goo.gl/w8sIlG (no need to open) but I have found something strange when I do the same but without changing the analysis...
Homework Statement
We did a Prac where we attached ticker tape to a cart (905g), and the cart to a mass (249g) through a pulley. We then had to assess the tape and answer questions. We are asked to calculate the force acting upon the whole system and then calculate the force acting only upon...
1. Homework Statement
Calculate the power lost in friction in the system shown above, with d=0.36, rpm=200, u=0.72, prop=1m and oil=0.23mHomework Equations
I know p=w/t comes into it in some form, either with other equations subbed in or a derivation somewhere, but not sure.
The Attempt at a...
If I'm designing an injector for a rocket engine, I have a specific mean flow rate (m/s) that must be met due to the pipe diameter and the required mass flow rate.
I've calculated all the pressure drops due to lost work from friction, valves, and orifice geometries (not from change in area, but...
Homework Statement
Two disks, rotating in the opposite direction of the other, are held together on their rotating ends, acting as toothless gears. The bottom disk is slightly skewed in one direction, and therefore causes a frictional force on the top disk, and thus an equal and opposite force...
Homework Statement
A block of mass ## M_1 ## is on an inclined plane (the plane is inclined at 30 degrees), and is attached with a light cord over a light, frictionless pulley to another mass ## M_2 ##. ## M_1 ## is fixed at 5.00kg, and ## M_2 ## can be varied.
When ## M_2 = 3.20 kg ##, ##...
I have a problem in analyzing movement with friction involved. I do not know how to correctly analyze systems as such and what is the correct view. I have tried to answer the several question below.
I have the following diagram. There is friction between all parts.
1) What force do we need to...
[mentor note: moved here from another forum, hence no homework template.]
A construction worker attempts to lift a uniform beam off the floor and raise it to a vertical position. The beam is 3.00 m long and weighs 372 N. At a certain instant, the worker holds the beam momentarily at rest with...
Homework Statement
Homework Equations
F=m*a
ΣF(n-direction)= m*a(n)= m*(v^2/ρ)
∑F(t-direction)= m*a(t)\
Ffriction= Fn*coefficient(of friction)
The Attempt at a Solution
So I tried solving this question and apperently it is way easier than I thought.
So I thought the kinetic friction has a...
Homework Statement
An 85 kg tobbogan that was originally accelerating at 3.0 m/s2 on frictionless snow hits a bare patch of concrete that exerts a force of friction on the sled of 180 N, what will the new acceleration be?
Homework Equations
F=maThe Attempt at a Solution
Ok so this was...
Imagine a car race about to take place. A car is starting at rest and when the timer goes off, the driver steps on the gas. The car starts off so fast, that its front wheels rise upwards so that all the weight of the car is held up by the 2 rear wheels. The car travels this way for a few...
I am sorry for drawing up very old and closed posting https://www.physicsforums.com/threads/rolling-friction.150891/
but I saw this question many times and I can not understand why do not people simply use well-known theorem which says that power of the forces which are applied to a rigid body...
I have two surfaces that have a coifficent of friction of .6. Disregarding mass (if possible) at what angle would the force of static friction and the normal force be equal
This is a two part question:
1. With a simple pulley system using one pulley - say 10000 kg on each side - the ability to pull either one up or down to change the position is theoretically just the friction on the system and any extra length of rope on one side?
2. Would it be more work lost...
Hello all,
I'm building a miniature vehicle and plan on using a DC motor that supposedly spins at 12800 rpm (1340 rad/s) for the engine. However, I'm a little confused as to what the car's acceleration would be. The DC motor on its own would instantaneously have an angular velocity of 1340...
As we all know, for the most part, the kinetic friction force is, for the most part, constant. After moving my cup across my table, this thought crossed my mind. If I move my cup across the table with a constant speed, then the force I'm applying must be equal to the kinetic friction force...
Homework Statement
An initially stationary box of sand is to be pulled across a floor by means of a cable in which the tension should not exceed 1100 N. The coefficient of static friction between the box and the floor is 0.35. (a) What should be the angle between the cable and the horizontal in...
A mass m1 is on a frictionless surface. To its right is a second mass m2 not touching the ground, but in the air. An applied force is applied towards the right of both masses. What is the minimum force needed so that the second object JUST starts to slip downwards...
[moderator note: moved from technical forums, no template]
this is fun but i am stuck. help! :) the first image states the problem and the second image is my futile attempt at a solution
Homework Statement
Hi, I was wondering how you would isolate for and calculate the coefficient of friction in an Atwood pulley, with one fixed pulley, with two masses hanging off of it on either side. There is no table or surface that the masses are touching or resting on, they are both...
at the beggining of basic mechanics, we learned about friction, moreover we distinguish between static and dynamic friction. there is something quite disturbing: when an object on an inclined rod is static we can say that the static friction is holding it in place. now, whe we push the object up...
Hello ,
I'm trying to model the forces on a needle being inserted in a tissue. Needle tip penetrates the tissue surface and as it moves through the tissue, it experiences friction from needle-tissue interaction. Friction arises from the pressure exerted by surrounding tissue as it grips the...
Homework Statement
Mass: .034kg
Acceleration: -.3644
Time:2.744sec
Inital Velocity: 1m/s
The path is on a flat surface
Homework Equations
Ff=mu(Fn)
F=m*a
The Attempt at a Solution
I need help find the coefficient of friction. I'm trying to find the difference of mu between oil, water, and a...
Homework Statement
A 25 kg bear slides, from rest, 8 m down a lodgepole pine tree, moving with a speed of 6.4 m/s just before hitting the ground
(a) What change occurs in the gravitational potential energy of the bear-Earth system during the slide?
W = F*D
W = (m*a)*D
W = 1960
(b) What is the...
The door is 4.5 lbs evenly distributed. Width is 7" and length is 19". The door is mounted by using a friction hinge at the center . How to calculate the total load acting on the hinge? What is the maximum load bearing capacity of the hinge? Length of hinge is 3.2" and diameter of pin is .230...
Homework Statement
the major loss in the fluid due to pipe friction is f(L)(v^2) / 2gD , (darcy weisbech equation)
why the author use 4fL(V^2) / 2gD ? in the equation ? is it wrong ?
Homework EquationsThe Attempt at a Solution
Homework Statement
Suppose a 180 kg motorcycle is heading toward a hill at a speed of 29 m/s. The two wheels weigh 12 kg each and are each annular rings with an inner radius of 0.280 m and an outer radius of 0.330 m.
How high can it coast up the hill, if you neglect friction in m?
*m = 180 kg...
Homework Statement
In the system, find minimum weight of the block 'B' to start the motion of the block 'A'
up the plane.weight of block 'A' 10 KN. The angle of friction for the block and the incline,between the pulley and the string may be assumed as 15° (assume pulley is locked)
Homework...
I understand that every force has an equal and opposite reaction, and the reason things can move is because the forces acts on different things. Also, F=MA is why the heavier object is accelerated less. The equal and opposite reaction to gravity pulling down towards the Earth's core on a book...
Homework Statement
The static co-efficient of friction between a football blocking sled (90 kg) and grass is 0.56. (i) If an80 kg coach stands on top of the blocking sled, what is the maximal static frictional force?(ii) Will the dynamic co-efficient of friction between the sled (with the coach...
Homework Statement
Sam, whose mass is 75 kg, stands at the top of a 12-m-high, 100-m-long snow-covered slope. His skis have a coefficient of kinetic friction on snow of 0.07. If he uses his poles to get started, then glides down, what is his speed at the bottom?
Homework Equations
v =...
So I'm trying to understand Newton's laws, and I know that friction is supposed to be the force that stops an object in movement. But I don't really understand why this is the case, as the force of friction is not something that can be perceived intuitively (unlike, for example, the force I...
Homework Statement
The block was given an initial velocity up the surface with an angle of 45 degrees to the ground. Calculate the ##\frac{t_1}{t_2}## with ##t_1## being the time it took to get to the highest point up the hill and ##t_2## the time it took to get down. In both cases the...
Lets say that there is a rectangular box on a horizontal surface, with no air resistance on it. If the applied force required to get the object moving is greater than the static friction, Fa>Us* Fn, then the object starts moving. However, the Static Friction is almost always greater than the...
Homework Statement
Homework Equations
PE at A = 3mgx
WD = Fs
KE = 1/2mv^2
The Attempt at a Solution
The question I am stuck on is part ii.
I worked out from part i that the PE at A is 3mgx, so therefore all this must go towards the KE and the sound, and doing work against friction, etc...
How does friction lose energy when the conservation of energy law doesn't allow energy to be lost ??
Sorry if this is a stupid question I have tried googling but can't find much to help.
What is the physics behind drawing dotted lines with chalk with just one stroke?
This is a video demonstrating this:
Here is what I currently have:
as soon as the applied force exceeds that of the frictional, the block will accelerate. What makes it slip though? Because there is a jerk...
We know that force * coeff. of friction = m * g. . It does not make sense. Pls read details. This is when force is applied perpendicular to the direction of friction. But suppose we say that m = 10 kg, g = 10 m/s2, coeff. of friction is 0.1. Then by formula it says that force required to keep...
Homework Statement
truck moves at 22,5 m/s
On board the truck, behind, is a box.
the static friction coefficient for the box, is 0,250 with regard to the friction between truck floor and the box floor.
calculate the shortest possible stopping distance, such that the box does not slide at...
When we talk about headloss in pipelines (which is defined with Darcy-Weisbach or manning or hazen-Williams equations) we talk about friction between liquid and pipe wall and we do not talk about moving molecules of water on each other. Does not it (moving liquid surfaces on each other)result...