Friction Definition and 998 Threads

Hi guys, Yesterday I sat down, and just for fun, decided to calculate the coefficient of kinetic friction for the all electric Ford Focus. I keep getting the wrong answer, and it is driving me crazy. Here are the facts. Battery: 23 kWh. Curb weight: 1,651 kg. Maximum travel distance before a...

Homework Statement A phonograph record is whiring around at 103 rpm. Two balls of mass 1 kg are sitting on the disk and are at rest with respect to disk. The first ball (1) sits at a radius 5 away from center. The second ball (2) sits at a radius of 10 away from center. What is the ratio of...

Homework Statement I don't remember exactly what the question was because it was on a quiz today. It said something along the lines of "a ladybug is on a turntable and begins to slip at .5 m/s. Find the coefficient of friction. Homework Equations Fc = (mv^2)/r a = v^2/r Ff = uFn I think...

Homework Statement Efficient and safe transportation depends on friction being either minimized or maximized as necessary. a) One example in which friction is maximized to aid in transportation a) One example in which friction is minimized to aid in transportation For each situation, explain...

I've just been thinking, and I don't know why I couldn't figure this out on my own, but I got this question bugging me. I was moving a sofa the other day. The sofa was against a wall. I started thinking why it was harder to push the sofa parallel to the wall when it was touching the wall rather...

If friction is independent of area of contact, how do less inflated tires of a bicycle experience more resistance towards motion than the well inflated tires?

Homework Statement What is the maximum acceleration the train can achieve? Engine effect=6500kW μ(Friction Coefficient (between rails and wheels))=0.45 g=9.82N/kg m(Train weight)=120,000kg α=0 Homework Equations Fμ=Fn*μ Fn=cos(α)*m*g a=F/m The Attempt at a Solution We've used the equations...

Homework Statement When a disk rolls in a surface whitout slip, the velocity of the disk's edge (where it contacts the surface) is zero with respect the surface and the friction force is less than the maximum allowable of Us.N, where Us is the coefficient of static friction and N is the normal...

Homework Statement I have no idea what torque of a friction in a bearing is. I'm looking for good explanation. Homework EquationsThe Attempt at a Solution I understand what torque/friction/bearing is. But I have no idea how they come together when looking at the actual mechanical problem. Help!

Homework Statement I have a sphere, it's imperfectly spherical, I put it on an incline and apparently it needs a minimum friction to start rolling or moving. Homework Equations I = 2/5 MR^2 torque = I*alpha = R x F The Attempt at a Solution [/B] before anything, I don't get why there's a...

Homework Statement A block of mass m is placed on a rough wedge inclined at an angle α to the horizontal, a distance d up the slope from the bottom of the wedge. The coefficient of kinetic friction between the block and wedge is given by µ_0x/d, where x is the distance down the slope from the...

A couple of forces act on the screw and create the turning effect. But after sometime it gets harder. So, net torque is decreasing, but why is it decreasing? Frictional force comes into action, but friction doesn't depend on surface area. So, frictional force will remain constant. So what...

Homework Statement Example 2.12 : A block pulled on a horizontal table with friction. A block of weight 100 Newtons rests on a horizontal table. The coefficient of static friction between the block and the table is µs = 0.8. a. If someone pulls on the block with a force F in the direction 37◦...

Hi So I am busy studying rotational motion and there's an example in the book where they explain that when a car brakes the force of friction acts as a torque force which explains why a car lifts up at the back when braking. Because the car does no rotational motion they say the net torque is...

Homework Statement A ladder of length 5 m is resting against a SMOOTH wall, its point of contact being just below a first floor window. The bottom of the ladder rests on the ground and the coefficient of friction between the ladder and the ground is 0.28 A person of mass 78 kg climbs the...

<< Mentor Note -- Two threads on the same subject have been merged >> I am a junior enrolled in IB Physics at the standard level at my high school. As a part of the curriculum we must perform an Internal Assessment (IA) which involves performing an experiment and performing calculations and it...

Homework Statement A 1500 kg car is traveling at a speed of 30.0 m s-1 when the driver slams on the brakes and skids to a halt. Determine the stopping distance if the car is traveling down a 10o slope. The coefficient of kinetic friction between the car and the road is 0.80. Homework Equations...

Homework Statement Determine the coefficient of friction for a surface when the mass of an object is 300g and the angle of incline when the object starts to move is 29° Distance traveled and acceleration are not provided Homework Equations W = mg Ffric = μN N = mg cos(θ) μN = mg sin(θ) The...

Homework Statement A student pushes a 0.65kg box Ali g a desk. When he stops pushing the book, it moves 85cm before stoping (slowing down in this period). Coefficient of friction between book and Table is 0.27.Calculate the work done on the book by the friction. Should it be positive or...

1. A crate resting on a rough horizontal floor is to be moved horizontally. The coefficient of static friction is 0.40. To start the crate moving with the least possible applied force, in what direction should the force be applied? a. Horizontal b. 24 degrees below horizontal c. 22 degrees...

Homework Statement Homework Equations W = Fk d cos θ Fk = FN μκ The Attempt at a Solution Here's my work : m = 1 kg vi = 10 m/s vf = 0 m/s xi = 0 m xf = 0.1 m d = 0.1 m k=60 N/m μκ=? The work done be the frictional force : W = Fκ d cos θ = FN*μκ*d*cosθ = mg μκ d cos 180 =...

Homework Statement Homework Equations W = ΔUg + ΔkE + ΔUs KE = 0.5 m v^2 Ug = m g h Us = 0.5 k x^2 The Attempt at a Solution k = 60 N/m vi=0 m/s (" the block is released from rest ") xi= 0 m/s ( "the spring is unstreached") vf= 0 m/s xf= 0.2 * sin 37 = 0.2*0.6 = 0.12 m d= 0.2 m...

I'm new to the forum and after some help if anyone can explain. I've read a few articles now, which have stated that the average co-efficient of friction for a tire with tread will be between 0.4 in the wet and 0.7 in the dry. If instead the tire had no tread, the co-efficient of friction will...

Im a high school student and am in AP Physics 1. I just created a formula for calculating the coefficient of kinetic/static friction between two objects using only distance and time (I don't have a way to measure Newtons). Is it correct and can it be used in the real world?

Hi Friends, So I'll go into a bit of the setup that I'm having some trouble figuring out. I have a piece of rubber that will be pushing up against the side of a metal (or plastic) container to create a waterproof seal. The easiest way to think about this would be to imagine the rubber piece of...

Homework Statement The coefficient of friction between A and the table is μA. The coefficient of friction between A and B is μB. A, B, C and D all move with an acceleration of 2m/s^2 (A and B move to the left). Find the force that the friction between the bodies apply on B. Find the tension of...

Homework Statement Homework Equations F = ma Fr = uK * N The Attempt at a Solution My answer is 7 but it is not one of the choices Thanks in advance[/B]

Hi everyone, Me and a friend discussed a problem relating to a rotating reference frame, and somehow got to this question which we can't fully figure out, or maybe we are missing something. so, here goes: On Earth's equator, our tangential velocity is ~1700 km/hr. A satellite orbiting right...

Homework Statement Another question with the same idea, These questions bother me a lot. Hopefully you can help me figure why they solve it this way. https://image.prntscr.com/image/aRnAD33ES2mML5JBwQBQvQ.png it said in the question that U = 0.6 without saying if it is static or kinetic...

Homework Statement You are presented with a circumstance in which three children are playing on a frozen pond. The three small children of mass 20.00 kg, 24.00 kg, and 16.00 kg, respectively, hold hands, and are pulled across a smooth frozen pond by a larger boy on skates, who pulls a...

Homework Statement For a project we have to find a movie scene and calculate using any variables we can find. I am using Back to the Future and want to calculate the distance the DeLorean travels in one of the first scenes when they're first using it. I'd also like to find the acceleration from...

Homework Statement If the car is going 30 m/s half way up the loop and loses energy due to friction at a rate of 2.0J per meter of track, how fast will it be going at the top? (this is question related to the loop of roller coaster track, with radius 20m.) Homework Equations 1. Ki + Ui = Kf +...

Homework Statement Sorry for the bad resolution on the image but I will clear the variables out. The friction act on points A and B, Us = 0.2, W = 900 and there is a force P to the right The question is: Find the force P that makes the weight move downward with a constant velocity Homework...

<Moderator's note: Moved from a technical forum and thus no template.> Here’s the question Design a simple expirament that you could carry out in your own home to i) determine coefficient of friction between your object and surface ii) prove that coefficient of static friction is only...

Homework Statement A coffee cup in your dashboard slides forward when you decelerate from 20 m/s to rest in 3.5 s or less, but now if you decelerate for a longer time. What is the coefficient of static friction between your coffee cup and your dashboard? Homework Equations a = delta a / delta...

Homework Statement An elevator is traveling at 30 m/s just as it touches a cushioning spring. The safety clamps engage at that moment and provide 20,000N of frictional force. The mass of the elevator is 3000kg and the spring constant is 15000 N/m. How fast will the elevator be traveling after...

I am doing some calculations to optimize the power to weight ratio and gearing of a RWD car. I have torque charts and can calculate the force put to the track by each wheel and the static frictional force by the track on each wheel. I am trying to determine what the minimum speed is for the...

Homework Statement 14.6 The coefficient of kinetic friction between the slider and the rod is μ, and the free length of the spring is ##L_0 = b##. Derive the expression for the work done by the friction force on the slider as it moves from A to B. Neglect the weight of the slider. Homework...

Homework Statement A coin stands vertically on a table. It is projected forward (in the plane of itself) with speed v and angular speed w. The coefficient of kinetic friction between the coin and the table is u. What should v and w be so that the coin comes to rest (both translationally and...

Homework Statement A 400N trunk is on a 20 degree inclined plane and has a coefficient of kinetic friction of 0.56. What force must be exerted on the trunk to make it slide down the plane at a constant velocity? Homework EquationsThe Attempt at a Solution I have drawn a free body diagram of...

Homework Statement A car giving a turn on a curve with 88m of radius, traveling at a speed of 95km/h, the curve is perfectly banked for a car traveling at 75 km/h, meaning that the curve has an angle θ of 26.7º. Homework Equations μ = ? r = 88m v = 26.38 m/s θ = 26.7º Ff = μ · g · m Fc = m...

Homework Statement [/B] A uniform solid disk of radius R is set into rotation with an angular speed ωi about an axis through its center. While still rotating at this speed, the disk is placed into contact with a horizontal surface and immediately released as shown in figure below (a) What is...

Homework Statement The question is as follows: A 50kg ice skater is gliding along the ice, heading due north at 4.0m/s. The ice has a small coefficient of static friction, to prevent the skater from slipping sideways, but kinetic friction =0. Suddenly, a wind from the northeast exerts a force...

Homework Statement A roller coaster reaches the top of the steepest hill with a speed of 7.0 km/h. It then descends the hill, which is at an average angle of 43° below horizontal and is 46.0 m long. What will its speed be when it reaches the bottom? Assume the coefficient of kinetic Friction...

Homework Statement A crate is being transported on a flatbed truck. The coefficient of static friction between the crate and the bed is 0.470. What is the minimum stopping distance if the truck, traveling at 70 km/h, is to decelerate uniformly and the crate is not to slide forward on the bed...

Homework Statement A worker is going to attempt to pull a 90-kg box across a level floor by a rope that makes an angle of 35° with the floor. The tension in the rope is gradually increased until the box just starts to move. If the coefficient of kinetic friction is 0.36 and the coefficient of...

Could anybody explain what happens at the molecular level when one of the two bodies in a contact starts moving w.r.t other, i mean in this process what causes kinetics friction force, i tried myself to think of it but i could not come up with any, so please help me.

At a force of 40N, the body moves along a horizontal surface with an acceleration of 2m/s^2 and under the action of 50N with an acceleration of 3m/s^2. What is the mass of the body? F1 = 40N a1 = 2m/s^2 F2 = 50N a2 = 3m/s^2 _____________ m=? 2. Homework Equations As there's no...

Homework Statement I am referring to this thread and question: https://www.physicsforums.com/threads/rotation-of-a-spool-about-rough-ground.295666/ Here is the problem, restated: Homework Equations ##\tau_{net} = I\alpha## ##\tau = Frsin(\theta)## ##F_{net} = Ma_{cm}## ##\alpha = a_{cm} /...

Here is problem I quickly made up: Suppose there is a ramp with a height of 6 meters and length of 12 meters. A block of 5 kg is pushed up to the top of the ramp with a constant velocity. The force of friction is 15 N. Here's the confusion: By using the non-conservative force work energy...