Friction Definition and 998 Threads

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 =...

What has the highest coefficient of kinetic friction, steel on polyethylene, rubber on polyethylene, or polyethylene on polyethylene?

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...

I think this question is not important and rarely noticed, but I'm still curious XD kinetic coefficient of friction is used when the applied force of static friction coefficient is less than than the force that we give, or less than or equal to the force that we give? sry for my bad english

Homework Statement A cube with 1 kg mass is put on top of a bigger cube with 3kg mass and 1 meter edges. If 10 N force is exerted on the bigger cube, while the maximum friction between the cube surface is 2 N, and g=10m/s^2 , then at one time the small cube will fall to the floor. The time...

Homework Statement I am trying to prove that the coefficient of static friction is equal to the tan of the angle of incline. (You can find the proof of this from ) I set the angle of incline as my independent variable and had an angle range from 10 to 37.5 degrees. After setting the slope to...

Homework Statement Two crates are stacked on top of each other on a horizontal floor. The coefficient of static friction between Box A and Box B is 0.6. The coefficient of static friction between Box A and the floor is 0.2. A force of 100 N is applied parallel to the floor on Box B. The boxes...

Homework Statement Two boxes each weighing 900 N are stacked on a horizontal floor. Box A is on the bottom, box B is on the top. The coefficient of static friction between box a and the floor is 0.3. A worker applies a force of 600 N to box b parallel to the floor, and the stack moves together...

Hi guys, I was wondering if it is possible to have a pure planar rotation of a rectangular-prism shaped rigid body on a planar surface when it is subjected to a planar point force at the tip. Is there any range for the point force such that it can not break the static friction force (so no...

Walter Lewin in his lecture says, a truck and a car on a road will start to slide at a same angle if their tyres are made out of identical material. I know that max. frictional force is proportional to normal force. and if normal force is dependent on mass. shouldn't the frictional force depend...

Hi all, I am very confused by this concept. As I searched online, all respondents say that friction decreases as angle increases because normal force decreases. BUT, they don't explain this phenomenon: A block on a ramp is static at certain angle, and after the ramp is raised by a certain...

Hello all, I am working on a few test scripts to test the life of a hydraulic cylinder. (It is a mechanically operated cylinder and has a positive displacement) The testing will involve thousands of continuous pump and retraction operations, due to which the temperature of the piston seal and...

Homework Statement we know that the formula of head loss is k(V^2) /2g , the k = 1 when the water is discharged from pipe to reservoir ...However , how if the water from pipe is released into atmosphere ? is it necessary to include the head loss due to exit ? if so , is the k still =1 ? in the...

If I wanted to calculate, say, the heat released during space shuttle re-entry, how should I do it? I know they provide the heat on their website, but if I wanted to arrive at the result just through calculation, would that be easy?

Homework Statement in my book , the author stated that the friction factor become maximum when the flow become turbulent ...However , according to the Moody Chart , we can know that the friction factor decreases from laminar to turbulent and then constant ... is the statement in the book wrong...

Homework Statement So I have to do a report about tennis and about the spin. I understand how the magnus effect works and how the ball will bounce but am still unable to figure out how the actual spin is created by the contact with the racquet and the moving ball Homework Equations T=Fr The...

What kind and value is the friction coefficient of tank tracks on the move, when force is applied forward in the direction of the tracks movement? Is the friction coefficient in that case, closer to kinetic/sliding coefficient or to a rolling resistance coefficient? What about the sideways...

1. The problem statement, all variables and given/known i am having problem of finding the major loss caused by pipe friction in this question. the formula of major loss is given by fL(V^2) / 2gD , how to get the total length of pipe so that i can gt the major head loss? . Relevant equationsThe...

1. Homework Statement A small cube is sliding on a round dish (see attached figure) . The cube is always in contact with the (vertical) edge of the dish (which prevents the cube from falling outside the dish itself). There is friction between the cube and the dish. The dish can rotate around...

In a situation like this, there are two equilibrium's, For just about to accelerate downwards: mgsinθ - Ffriction - T = 0 For just about to accelerate upwards: T - Ffriction - mgsinθ = 0 Is there a situation where there is no static friction i.e. when mgsinθ = T?

Homework Statement Box B has initial velocity v0 and collides plastically but without clinging to mass A which is at rest. The spring, initially, is loose. assume that the collision time is very short. What's the boxes's velocity immediately after the collision? At what distance from the wall...