Friction Definition and 998 Threads

Homework Statement Using the results from problem 2.18 for the setup shown in the Figure below show that if the system is to remain at rest, then the coefficient of friction:a) between the stick and the ground must satisfy $$ μ ≥ \frac {sin(Θ)cos(Θ)} {(1+cos(Θ))(2-cos(Θ))} $$ Homework...

Homework Statement We have an inclined plane with a mass ##M## and an angle ##\alpha## and a box of mass ##m## over it. Everything is at the instant 0 (it's a problem of static, no dynamics). a) What's the acceleration in the component x of the box? b) What's the acceleration in the component y...

Friction is said to be a non conservative force. And I see various sources state that work done by a non conservative force on a round trip is always non zero. But is that always true? In a case where a coin is placed on a turn table, and the table is rotated, and the coin does not move during...

I am not sure how to approach a problem involving the friction coefficient when only given initial velocity, final velocity, and distance traveled. I could combine the friction and kinematic equations, but I am only familiar with doing that for one velocity... Here is the specific problem I had...

Homework Statement A hollow cylinder with mass m and radius R stands on a horizontal surface with its smooth flat end in contact the surface everywhere. A thread has been wound around it and its free end is pulled with velocity v in parallel to the thread. Find the speed of the cylinder...

1) What is friction loss / are friction losses? 2) How can it be determined / measured / calculated / figured out? 3) How does it affect the power output (force * speed) of an electric motor when an electric motor is moving / lifting objects? Why does it have such affects?

Homework Statement A box slides on a smooth (frictionless) horizontal surface, 1.50 m above the floor, at a speed of 2.00 m/s. The box then slides down a ramp that makes an angle of 36 deg with the horizontal and has a coefficient of kinetic friction equal to 0.430. After reaching the end of...

Homework Statement A cord connected at one end to a block which can slide on an inclined plane has its other end wrapped around a cylinder resting in a depression at the top of the plane as shown in (Figure 1) . Determine the speed of the block after it has traveled 1.60 malong the plane...

friction is causes the circular motion in the car around a curve, and if we draw free body diagram we will see the friction force must be opposite the car motion so the force of friction not toward to the center of the curve ,so the force of friction must be not the centripetal force ,mustn't it?

Homework Statement A 3.0 kg block is released from the top of a rough ramp of length 2.0m and accelerates down the ramp at 1.6m/s^2. If a force of kinetic friction of 10 N acts on the block, what is the angle of the ramp. Homework Equations Fnet=ma ff=(mu? I don't have that symbol HAHA) muFn...

Suppose there are two discs held in contact such that they rotate around the same axis of rotation. A torque is applied to one of the discs, and due to friction the other disc accelerates. Using calculus I found the torque applied due to friction for a disc to be ##\frac {2μF_N r} {3}##, meaning...

Homework Statement A cylinder of mass M and radius R rolls without slipping on a plank that is accelerated at rate A. Find the acceleration of the cylinder. Homework EquationsThe Attempt at a Solution Physical force acting on the system : Fphy = N + mg + fr w.r.t. plank frame i.e non -...

Homework Statement Ans: c) Homework EquationsThe Attempt at a Solution I can solve this problem if only I understand the setup . I am sure the diagram is missing something . Can someone help me understand the problem statement in context of the setup ?

Homework Statement A fireman of mass m slides a distance d down a pole. He starts from rest. He moves as fast at the bottom as if he had stepped off a platform a distance h≤d above the ground and descended with negligible air resistance.What average friction force did the fireman exert on the...

I have been reading quite a lot about the Physics behind car dynamics and I have gotten to a point which keeps confusing me, namely - brake locking. I understand brake locking as the situation when the wheels of the car do not rotate anymore but the car is still moving - this causes the tires...

Homework Statement Hi! I'm having issues with this practice problem. Any advice on what I'm doing wrong would help! A 2.5 kg particle is projected with an initial speed of 3.3m/s along a surface for which the coefficient of friction is 0.7. Find the distance it travels given that the particle...

Homework Statement A steel washer is suspended inside an empty shipping crate from a light string attached to the top of the crate. The crate slides down a long ramp that is inclined at an angle of 38 ∘ above the horizontal. The crate has mass 239 kg . You are sitting inside the crate (with a...

Hello all, I was driving down the road yesterday, and I realized that I don't really have a solid grasp on how frictional forces cause infrared radiation. Can anyone explain, or direct me to a resource that explains, how this happens at the atomic level? I am thinking that the work done...

Homework Statement Determine a formula for the acceleration of the system shown in the figure(Figure 1) in terms of mA, mB, and the mass of the cord, mC. Assume f to be the fraction of the cord that is hanging down between mB and the pulley, and μk to be the coefficient of kinetic friction...

Homework Statement A student is cleaning a block board by moving a light duster up and down as shown. (Coefficient of friction between the duster and board is ##MU## The duster will not move no matter how large the force is if ? Homework Equations No equations given The Attempt at a Solution...

Homework Statement They ask for the smallest force P to apply if neither block is to slip. Coeff. of friction given as 0.25. The 20KG block is 196N; the 10KG block is 98.1N [/B]Homework EquationsThe Attempt at a Solution [/B] If we start at the 10KG block: Sum of forces x: N + cos26.6P –...

I have few (more or less) general questions: 1. I know that: "The coefficients of friction are nearly independent of the area of contact between the surfaces". I understand this, but I know from everyday life, when car tire tread is worn off, braking distance increases and maximum acceleration...

Today I've come across the statement that the coefficient of static friction of rubber tires on asphalt is bigger than that of tires on concrete. Does it mean that the maximal acceleration a car can attain on asphalt will be greater than that on concrete? My assumptions: 1)The force of friction...

Homework Statement [/B] A hockey puck travels across the ice at 6.5m/s. the puck travels a total of 7.6m. What is the coefficient of friction between the puck and the ice. Homework Equations [/B] fnet=ma Ffr= coefficient of friction x force normal The Attempt at a Solution [/B] I found my...

a massless pulley with friction between its surface and the string passing over it .If string is having two unequal masses connected to it on both side of pulley then will the pulley rotate?

Homework Statement I do not fully grasp the concept behind all of these sub questions (i)-(iv). Homework Equations v=wAcos(wt) (SMH)? Friction Force = Coefficient of Friction * Normal Force The Attempt at a Solution (i) Varying as simple harmonic motion sees varying acceleration as it...

Hi I was wondering if someone could tell me the equation for finding out what the windage and friction losses are based on the information below. I've drawn the graph and I can work out the I/0, R0 and X0A four-pole, star-connected, squirrel-cage induction motor operates froma variable voltage...

Lets say there is a pulley attached to the ceiling. Hanging on the pulley is a rope and on each end is a 1000 lb. weight. I believe that theoretically it wouldn't take any torque at all to rotate the pulley if it were frictionless (maybe inertia would play a role, but let's ignore that)...

Hi, I've built a coilgun using a solenoid, but my projectile stops at the half of the road, but this way i can't measure neither the acceleration nor the speed. what could be wrong ? how to push it further ? I also have a question about the efficient methods to measure the speed of the...

Where do I find a good comprehensive table of friction coefficients between various materials? I'd like, in particular, to be able to compare the coefficient of static friction between tungsten carbide and sapphire and that between sapphire and sapphire. Tables that I have found tend to have...

Homework Statement Calculate the deceleration of a snowboarder going up a 5.0° slope, assuming the coefficient of friction for waxed wood on wet snow ( = 0.1). Homework Equations F = ma W = mg Fs = (Fn) Fk = k (Fn) The Attempt at a Solution Answer key says it's 1.83 m/s2. I fiddled...

Homework Statement A Chinook helicopter’s rotor blades and hub have a top speed of 300 revs/min and a combined mass of 300 kg. On a maintenance test the blade assembly is allowed to stop without applying the brake, in this condition the blades take 48 seconds to come to a standstill. The...

If a body is moving in one constant direction, is it considered stationary with respect to other directions? For example, consider a table. Let the surface of the table be defined by an x-y Cartesian plane. If the body is moving in the x direction on the table, and a force (< (μs * Fn)) is...

Homework Statement It's Problem 3 of this page: http://www.problemsphysics.com/forces/inclined_planes_problems.html "A box of mass M = 10 Kg rests on a 35° inclined plane with the horizontal. A string is used to keep the box in equilibrium. The string makes an angle of 25 ° with the inclined...

hilbert2 submitted a new PF Insights post Damped Motion in Classical and Quantum Mechanics Continue reading the Original PF Insights Post.

<< Thread moved from the technical forums so no Homework Help Template is shown >> Hello, I'm attempting an experiment where I take a cart and slide it down a ramp. Each time, I will coat the ramp with a different liquid. I want to compare the effects of the dry ramp, a ramp with water poured...

Homework Statement A wheel of radius R rolls along the ground with velocity V. A pebble is carefully released on top of the wheel so that it is instaneously at the rest on the wheel. Show that in the case ##V < \sqrt{Rg}## and the coefficient of friction is ##\mu = 1## the pebble starts to...

Hi everyone: I need the brain of an engineer if anyone out there cares to help. I have a masters in Math from UofT but could use some knowledge from the smartest people- Engineers, I am now an experienced builder and yes everyone, we need smart people doing construction too- my math degree has...

Homework Statement There's two blocks of mass m_{A} and m_{B} which are linked by an ideal string. The block of mass A descends at constant speed. There's no friction. If the pulley is ideal, which one of the following is true[/B] Homework Equations Newton laws and trigonometry I...

Hey, I am doing some research on the brachistochrone problem WITH frictions. I found the following demonstration on the web. The beginning is ok. But I can't understand how the managed to pass between (29) and (30) and between (30) and ((32), (33)). If someone could help me, it would be very...

I teach a first year Physics course. The incoming students (grades 10-12) have little to no Physics background. We are making some modifications to our work and energy unit. One modification that has been discussed is what to do about kinetic friction. At present, we account for friction as a...

A 30-cm-diameter, 1.6 kg solid turntable rotates on a 1.4-cm-diameter, 450 g shaft at a constant 33 rpm. When you hit the stop switch, a brake pad presses against the shaft and brings the turntable to a halt in 15 seconds. How much friction force does the brake pad apply to the shaft? I am...

Background question: A bicycle and rider have a combined mass of 75 kg. They freewheel down a slope whose maximum height is 6 meters above sea level. The slope is 20 meters long. At the end of the slope, the bicycle and rider are traveling with a velocity of 10 m/s. Calculate the work done...

I'm interested in finding out what the coefficient of friction would be for a few different materials such as:Copper on aluminum Copper on graphite graphite on aluminum I'm not sure if it matters if the order is reversed such as Aluminum on copper vs copper on aluminum.. also I've seen that...

So... I've been thinking in time manipulation "super powers" for at least three years. First i just thought "well, you have to drain time from things, don't you?" then i learned basic physics and i thought "well... that was kind of unrealistic, one actually should accelerate to a % of the speed...

Homework Statement Homework Equations The block has potential energy U at the top of the ramp, and this is transferred to kinetic energy K at the bottom, which is then trasnfered to work done by friction, Wfr. U = K Conservation of energy K = Wfr Conservation of energy g = 10 m/s2The Attempt...

Homework Statement A car drives along a curved track. The frictional force exerted by the track on the car is: a. greater than the frictional force exerted by the car on the track b. directed radially outward c. opposite in direction to the frictional force exerted by the car on the track d...

Homework Statement A box of mass m is set on a merry-go-round of radius r with a linear speed v. The friction coefficient between surfaces is μ. Homework Equations ac = v²/r The Attempt at a Solution I imagined this problem because I'm trying to understand more deeply circular motions. I have...

Homework Statement Homework Equations Sum of forces and moments The Attempt at a Solution Not getting the right answer. Dont know where I went wrong.

I'm studying boundary layers. I am confused by what I am reading in this book. The book says the friction force (F) per unit volume = $$\frac{dF}{dy}=\mu\frac{d^2U}{dy^2}$$ They say $$\frac{dU}{dy}=\frac{U_\infty}{\delta}$$ This makes sense to me, delta is the thickness in the y direction...