What is Kinetic friction: Definition and 509 Discussions
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
Note - I have used (uk) as the symbol for co-efficient of kinetic friction (mew k?).
You want to measure (uk) between snow and your snowboard. You measure the angle x the slope makes with the horizontal. You kick your snowboard so it slides up the slope, and then back...
I have some confusions between static friction and kinetic friction:
When the static friction equals to applied force on an object, an object doesn't move and stays at rest I think. How about if the static friction is larger than the applied force? Will the object still stay at the rest, that...
Homework Statement
You have been called to testify as an expert witness in a trial involving an automobile accident. The posted speed limit was 70 km/h . The driver of the car slammed on his brakes, locking the wheels, and left skid marks as the car skidded to a halt. You measure the length...
Homework Statement
A 16.5 kg sled is being pulled across a horizontal surface at a constant velocity. The pulling force has a magnitude of 82.0 N and is directed at an angle of 30.0° above the horizontal. Determine the coefficient of kinetic friction.
Homework Equations
The Attempt...
Homework Statement
Blocks 1 and 2 of masses m1 and m2, respectively, are connected by a light string. These blocks are further connected to a block of mass M by another light string that passes over a pulley of negligible mass and friction. Blocks 1 and 2 move with a constant velocity v down...
Homework Statement
If you use a horizontal force of 30.0 N to slide a 12.0-kg wooden crate across a floor at a constant velocity, what is the coefficient of kinetic friction between the crate and the floor.
Homework Equations
Fkf=μFn
The Attempt at a Solution
Im not sure how to...
Homework Statement
Consider the system shown in the figure. Block A has weight w_A and block B has weight w_B Once block B is set into downward motion, it descends at a constant speed.
Calculate the coefficient of kinetic friction between block A and the table top.
A cat, also of...
Homework Statement
Joe, whose mass is 80kg, takes off across level snow in his jet powered skiis. The skiis have a thrust of 186N and a coefficient of kinetic friction on snow of 0.1. Unfortunately, the skiis run out of fuel after only 8 s. What is Joe's top speed? How far has Joe traveled...
Homework Statement
Harry pulls a sled with a mass of 110kg along a level surface of the forest in a straight line at a constant velocity. What is the coefficient of kinetic friction between the surface and the sled?
Homework Equations
f_k = \mu_k N
Fg=ma
The Attempt at a Solution
I...
Homework Statement
A force sensor is used to measure a force applied to a 8.2 kg box on a hard, horizontal surface. It records that the box starts to move when the force is equal to 20.7 N. This force makes the box start to move with an acceleration of 0.4 m/s2. Find s and k respectively...
1. Comment on the difference (if any) between the slopes of the lines of best fit and the tangents of the angles of incline.
In my data i got that the static friction slope was 4N/kg and the kinetic was 2.2N/kg. and i think that we're supposed to divide that number by the gravitaional field...
I would really appreciate it if anyone could help me with this problem.
A baseball player slides into third base with an initial speed of 8.50 m/s. If the coefficient of kinetic friction between the player and the ground is 0.44, how far does the player slide before coming to rest?
I'm not...
Homework Statement
An 60-kg skier is sliding down a ski slope at a constant velocity. The slope makes an angle of 11° above the horizontal direction.
(a) Neglecting any air resistance, what is the force of kinetic friction acting on the skier?
(b) What is the coefficient of kinetic...
The way I approached the problem I found acceleration using V^2=vo^2 + 2ax. Then I set uk*mg = ma. The masses cancel... so its uk*g = a. I keep getting the wrong answer. What am I doing wrong?
Homework Statement
A hockey puck on a frozen pond with an initial speed of 22.3 m/s...
Homework Statement
A block whose weight is 30.0 N rests on a horizontal table. A horizontal force of 48 N is applied to the block. The coefficients of static and kinetic friction are 0.650 and 0.420 N, respectively. Will the block move under the influence of the force, and, if so, what will be...
Homework Statement
A box of books weighing 300 N is shoved across the floor of an apartment by a force of 400 N exerted downward at an angle of 35.2 degrees below the horizontal. If the coefficient of kinetic friction between the box and the floor is .570, how long does it take the box to...
Homework Statement
The block is pushed to the right at a constant velocity. If the coefficient of kinetic friction is 0.5, what is the magnitude of the pushing force?
Homework Equations
I don't know...
The Attempt at a Solution
SOS!How do you fing the coefficient of kinetic friction? SOS!
Can someone help me I am trrying to find the coefficient of kinetic friction
A 29 kg ox slides down a 30degrees ramp w/ an acceleration of 1.25m/s^2
the acceleration of gravity is 9.81m/s^2
please help i need this help in IF...
Homework Statement
A 1500 N crate is being pushed across a level floor at a constant speed by a force F of 700 N at an angle of 20° below the horizontal.
What is the coefficient of kinetic friction between the crate and the floor?
Homework Equations
f=mu(n)The Attempt at a Solution
I tried...
Here is the problem:
A hockey puck is hit on a frozen lake and starts moving with a speed of 13.0 m/s. Five seconds later, its speed is 5.20 m/s.
(a) What is its average acceleration?
I used the kinematic equation V=Vo+at to find the accerlation which came out to be -1.56 m/s^2...
In my book, static friction means The frictional force that must be overcome to start one surface moving over another. Kinetic friction means the force that opposes the motion of one surface over another. My teacher said that a wheel rolling is a static friction, and it's weaker than sliding...
Homework Statement
A 98 N box of oranges is being pushed across a horizontal clean steel surface until it stops. As it moves, it is slowing down at a constant rate of 1.1m/s each second. The push force has a horizontal component of 25N and a vertical component of 20N downward. Calculate the...
Homework Statement
You push a 2.0 kg block against a horizontal spring, compressing the spring by 15 cm. When you release the block, the spring forces it to slide across a tabletop. It stops 75 cm from where you released it. The spring constant is 200 N/m. What is the coefficient of kinetic...
Hi, can someone please give me hints as to how to do this problem?
A 12 kg block is released from rest on an 36 degrees inclined plane and moves 2.4m during the next 4.2s. What is the coefficient of kinetic friction for the incline?
I know that the normal force = mgcos(delta), and...
So the problem states:
A 1.4 kg wood block is launched up a wooden ramp that is inclined at a 22 deg angle. The block's initial speed is 14 m/s. Use Uk = 0.20 for the coefficient of kinetic friction for wood on wood.
U = mu...
(a) What vertical height does the block reach above its...
This really isn't a homework question -- but it does involve my homework. Say you've got a box sliding down an incline of x degrees at a constant speed, I somehow got that that coefficient of kinetic friction is equal to tan(x). Will this always hold true for objects moving at a constant speed...
i need help to find the way to solve this problem involving friction...
find the minimum time in which a car whose initial speed is 30 mi/h can come to a stop on a wet road where the coefficient of kinetic friction is .5
Homework Statement
The figure shows 3 crates being pushed over a concrete floor by a horizontal force f of magnitude 440N. The masses of the crates are m1=30 kg, m2=10kg, and m3=20kg. The coefficient of kinetic friction between the floor and each of the crates is 0.7. what is the magnitude F32...
Here is the problem: A block is released from rest on an inclined plane and moves 3.5 m during the next 4.8 s at an angle of 31 degrees. The acceleration of gravity is 9.8 m/s^2. What is the magnitude of the acceleration of the block? what is the coefficient of Kinetic Friction Muk for the...
Homework Statement
Losing Cargo. A box of mass m rests on the flat floor of a truck. The coefficients of friction between the box and floor are "us" and "uk". The truck stops at a stop sign and then starts to move with an acceleration of a. If the box is a distance x from the rear of the...
Homework Statement
a box is dropped onto a covoyer belt moving at 2 m\sec .if the coefficient of friction between the box &the belt is 0.4 ,how long before the box moves without slipping ?
Homework Equations
F(friction)=N(normal reaction) X coefficient of friction
The Attempt at a...
Real Life Situations?
Hey everybody. I was just wondering if there are any real life situations where the static friction of an object will ALWAYS be greater than the kinetic friction. Please let me know! Thanks!
-J
"A child rides a wagon down a street with an inclination angle of 38.0 degrees. In order to keep from moving to fast, the child has secured the wheels of the wagon so that they do not turn. The wagon and the child then slide down the hill at constant velocity. What is the coefficient of kinetic...
Hi, I'm having problems solving this problem:
A small box of mass m1 is sitting on a board of mass m2 with length L . The board rests on a frictionless horizontal surface. The coefficient of static friction between the board and the box is us. The coefficient of kinetic friction between...
you are driving a 1500 kg car at a constant speed of 20 m/s along Grand Blvd. a wet road, asphalt level road. as you approach the intersection, you get a call on your cell phone. then you forgot about the stop sign. when you see the stop sign you slam on the brakes 20 meter from the...
A sight on many "bunny" hills across ontario is young skiers pushing on ski poles and gliding down a slope until they come to rest. Observing from a distance, you note a person 25kg pushing off with the poles to give an initial velocity of 3.5 m/s. If the inclination of the hill is 5 degrees and...
Please help me solve this problem :confused:
A girl coasts down a hill on a sled, reaching level ground at the bottom with a speed of 7.0 m/s. The coefficient of kinetic friction between the sled's runners and the hard, icy snow is 0.050, and the girl and sled together weigh 645 N. How far...
Kinetic Friction Problem..Need Help!
Okay...so I really think I'm doing this right..but the CAPA thing won't take my answer so there has to be something I'm doing wrong.
The Question is ...
A 32.0 kg box is being pulled along a horizontal surface by means of a rope that exerts a force of 265...
Coefficient of kinetic friction
:confused: so I am working on the force of friction and overcoming friction
i know that the coeffcient of friction is equal to the kinetic force over the normal force and i can get these when hte system is on a horisantal surface
But i don't understand how to...
hi everybody.. can i ask how to get a coefficient of kinetic friction if a 20 kilogram sled is being pulled across a horizontal surface at a constant velocity. The pulling force has a magnitude of 80 Newton and is directed at an angle of 30 degrees above the horizontal. please answer my...
I am very confused about this problem. The given info is:
You are standing at the bottom of an 8 m long ramp that is incline 37 degrees to above the horizontal. You grab a package from a conveyer belt and push it up the ramp. The coefficient of kinetic friction is 0.30
The questions:
1. What...
Hey,
New here so I don't know if I'm posting this in the right area if I'm not please redirect me. I have this lab on static and kinetic coefficients of friction. One of the discussion questions is what are the expected or known values for wood against rubber and steel against wood. Basically...
A 30.0 kg seal at an amusement park slides down a ramp into the pool below. The top of the ramp is 1.60 m higher than the surface of the water and the ramp is inclined at an angle of 30.0° above the horizontal. The seal reaches the water with a speed of 4.90 m/s. What is the work is done by...
To move a large crate across a rough floor, you push down on it at an angle of 21°. Find the force necessary to start the crate moving, given that the mass of the crate is m = 32 kg and the coefficient of static friction between the crate and the floor is 0.57.
N=mg=(32)(9.81)= 313.92 *...
I don't get it, first of all, why does air friction quadruples as velocity doubles? Second, if that air friction works in that way, why does kinetic work in a constant manner?
how to find coefficient of kinetic friction... please?!
I am lost on this question, hopefully someone can help:
a 300 kg crate is placed on an adjustable incline and as one end of the incline is raised the crate begins to move downward; if the crate slides down the plane at an acceleration...
Suppose that the coefficients of static and kinetic friction have values such that the static coefficient is twice the value of the kinetic coefficient for a crate in contact with a cement floor. Does this mean that the magnitude of the static frictional force acting on the crate at rest would...
A box with mass M is dragged across a level floor having a coefficient of kinetic friction (greek mu)k by a rope that is pulled upward at an angle Theta above the horizontal with a force of magnitude F.
What is the expression of the mag. of force needed to move the box with a constant speed...