Kinetic friction Definition and 504 Threads

Homework Statement The record speed for grass skiing was set in 1985 by Klaus Spinka, of Austria. Suppose it took Spinka 6.60 s to reach his top speed after he started from rest down a slope with a 34.0° incline. If the coefficient of kinetic friction between the skis and the grass was 0.198...

Why would the coefficient of kinetic friction be larger for an inclined plane versus a horizontal plane? Would it be related to the material? I thought initially it was something to do with the force of gravity… but apparently that's not it :( Thanks so much in advance!

Thanks everyone for your help.

Homework Statement The 40 kg crate shown in the Figure below rests on a horizontal plane for which the coefficient of kinetic friction is mk = 0.3. If the crate is subjected to a 350 N towing force as shown, determine the speed of the crate 3 seconds after starting from rest. + given angle of...

Homework Statement A person pulls a box (m=10 kg) horizontally with +2m/s2 acceleration by applying 45 N force. The displacement of the box is 8 meters from initial position. a) How much work is done by applied force? b) How much work is done by kinetic frictional force? Homework Equations Wf...

A 250-N force is directed horizontally as shown to push a 29-kg box up an inclined plane at a constant speed. Determine the magnitude of the normal force, FN, and the coefficient of kinetic friction, µk. So, I know I have to find the vertical and parallel forces Vertical: Fn and 250 sin of...

Homework Statement There is a hemispherical dome that sits on a horizontal plane. It has a radius of 10m. A 2 kg block sits on top of the dome. Pt. 1: Assuming the coefficient of kinetic friction is 0, at what angle, θ, will it leave the dome? Pt. 2: Assuming that μk is 0.3, what is the...

A 250-N force is directed horizontally as shown to push a 29-kg box up an inclined plane at a constant speed. Determine the magnitude of the normal force, FN, and the coefficient of kinetic friction, µk. FN µk (a) 330 N 0.31 (b) 310 N 0.33 (c) 250 N 0.27 (d) 290 N...

Hi guys, i have some questions regarding Frictional Force that came up in a book. If the cube moves throgh a distance of 4.0m in 2.0s, find the kinetic friction and coefficient kinetic friction between the cube and the plane. ( coefficient of static friction force Us= 0.466, angle of incline=...

Homework Statement A car is traveling at a given velocity on a road with a coefficient of friction of 0.5 when it suddenly has to apply the brakes. Given that it travels 10 meters before coming to a stop what is the initial velocity of the car? Homework Equations Vi^2=Vf^2 + 2ax...

Homework Statement Find the applied force for a object if the coefficient of kinetic friction equals 0.30 and the acceleration equals 5m/s^2. The applied force makes a 40 degree angle with the horizontal. The mass of the object is 10kg. Homework Equations Fnet=ma The Attempt at a...

Homework Statement A 100 N force directed 37° below the horizontal is applied to a 30 kg object on a horizontal surface. If the magnitude of the acceleration of the object is 1.3 m/s2, what is the coefficient of kinetic friction (μk) between the object and the surface? Homework Equations...

Homework Statement A computer scientist has dropped a tiny pizza crumb onto a magnetic disk. Later, when it's turned on, the disk is rotating at 88 revolutions per second about its axis, which is vertical. The coefficients of kinetic and static friction between pizza crumbs and the disk are...

"A hockey puck is hit on a frozen lake and starts moving with a speed of 12 m/s. Exactly 5.0 s later, its speed is 6.0 m/s. What's the puck's average acceleration? What is the coefficient of kinetic friction between the puck and the ice?" I've calculated the acceleration, but I'm stuck when it...

A 10kg block is at rest on the floor, and then a force of 30 N pushes on the block horizontally. If the coefficient of static friction between the block and the floor is μs= 0.33 and the coefficient of kinetic friction between the block and the floor is μk= 0.20, what is the acceleration of the...

A 4700 kg truck carrying a 900 kg crate is traveling at 25 m/s to the right along a straight, level road, as shown below. Suppose the brakes are applied for 3.0s. During this 3.0s the truck travels 55 m. 1. Calculate the acceleration of the truck during the 3.0s interval. (Assume it is...

Homework Statement Question in entirety: Vladimir Putin has contacted you to redesign the ski jump at the Olympic games. In the ski jump, contestants begin at rest at the starting gate on top of a hill inclined at an angle of 30 with respect to horizontal. They then accelerate down the hill...

Homework Statement A crate of bananas has an initial speed of 4.2 m/s2. It slides across a floor, traveling 6.0m before coming to a stop. Find the coefficient of kinetic friction between the crate and the floor. Homework Equations Fnet=ma v2=v02+2aΔx The Attempt at a Solution...

This isn't homework. I'm reviewing physics after many years of neglect. As with most of my posts, I made this problem up. Let object A have mass m_A and object B have mass m_B. One of A's surfaces is flat, as is one of B's. These flat surfaces are in contact and slide relative to each other...

In my textbook, there is a problem that made me think a bit more (this is not what the textbook was asking). In the problem, there is a 1500 kg car traveling at 30 m/s on a 10 degree sloped hill (the car is driving uphill). The driver slams on the brakes and skids to a halt. We have to...

Hello everyone, I would appreciate some help with this problem: The coefficient of kinetic friction between the 1.2 kg block in the figure below and the table is 0.38. What is the acceleration of the 1.2 kg block? Homework Equations F=M*A Fk = μk * N The Attempt at a Solution I created...

Can anyone explain this case ? If a moving box is pulling with a force F and the kinetic friction is 0.4F, of course, it will move in the direction of applied force with an acceleration and the net force is 0.6F But what if the force suddenly decreases to 0.3F ? The box is still moving so the...

Homework Statement An electric motor is used to pull a 125kg box across a floor using a long cable. The tension in the cable is 350N and the box accelerates at 1.2 m/s/s [fwd] for 5.0s. The cable breaks and the box slows down and stops a )Calculate the coefficient of kinetic friction...

Homework Statement There's no specific problem statement but I have to explain how I would find out the coefficient of kinetic friction given the angle (θ) of the inclined plane and mass of the object sliding down, nothing else. Homework Equations ƩF = ma μk = Fk (kinetic friction) / Fn...

Homework Statement A block is pushed across a horizontal surface with a coefficient of kinetic friction of 0.15 by applying a 150 N horizontal force. The block accelerates at 2.53 m/s^2. Find the mass of the block. Homework Equations ƩF = ma The Attempt at a Solution μk = 0.15...

Homework Statement A block is projected up an inclined plane that makes an angle θ to the horizontal. It returns to its initial position with half its initial speed. What is the coefficient of kinetic friction between the block and the plane in terms of the angle of the incline...

A hockey puck on a frozen pond with an initial speed of 12.3 m/s stops after sliding a distance of 198.9 m. Calculate the average value of the coefficient of kinetic friction between the puck and the ice. So I started with finding the acceleration. I divided 12.3m/s by 198.9m then took the...

"A driver makes and emergency stop and locks up the brakes of the car, which skids to a stop on dry concrete. Consider the effect of rain on this scenario. If the coefficients of kinetic friction for rubber on dry and wet concrete are μk (dry)=0.80 and μk(wet)=0.50, how much farther would the...

Homework Statement A 4.5 kg block is on an incline with a coefficient of static friction of 0.50. The angle that the ramp makes with the horizontal is increased gradually, until the block begins to slide down the ramp. If you know that the coefficient of kinetic friction between the block and...

Homework Statement A block of mass m is at rest at the origin at t=0. It is pushed with constant force F0 from x=0 to x=L across a horizontal surface whose coefficient of kinetic friction is μk=μ0(1−x/L). That is, the coefficient of friction decreases from μ0 at x=0 to zero at x=L...

A 23.5-kg rock is sliding on a rough, horizontal surface at 9.15 m/s and eventually stops due to friction. The coefficient of kinetic friction between the rock and the surface is 0.180. What average power is produced by friction as the rock stops? I think that the way to solve it is use...

Homework Statement I am conducting an experiment to determine the coefficient of static and kinetic friction between 2 objects I've arbitrarily chosen. I have a block and a plank of wood. I have been raising the plank to an incline to determine at what angle the block will begin sliding. I...

Homework Statement Mildred pulls a sled loaded with beer along a horizontal surface at constant velocity, as Bubba told her he needed it for he and his buddies to watch the football game. If the sled and beer in it has mass = 75 kg, the coefficient of kinetic friction μk between the runners...

Hello, I was competing calculations for a simple machine lab, and I got a different mu_k for 3 separate inclines of 20,30 and 40 degrees. But a question asks says ,"explain why the coefficient of kinetic friction should be independent of the inclination angle of the inclined plane." How do I...

Why is (Kinetic friction)= fk≤fs (Static friction) ? I understood the "equal to" case but how is the "less than" case possible? Similarly is this related to why is μk≤ μs ?

Hello, I am stuck on this question, I don't understand what to do. Any help would be great! I know that I have to use Newton's Second Law in the x and y directions. Greezy is pushing a very large crate of 50 kg across the floor at a constant velocity with a force of 200N. He is pushing on...

please help! The formula for kinetic friction acting on a sliding body is μkN When the body is sliding with constant velocity down an inclined plane fk=μkN When the body is sliding up the inclined plane(say due to a force acting parallel to the inclined plane) with constant velocity...

Homework Statement A child's slide is flat, 5 meters long, and sloped down so that the top is 3 meters higher than the bottom. A child slides down, starting from rest, and has v = 6 m/s at the bottom. Find the coefficient of kinetic friction, μk is: Homework Equations F=ma f=μkFN...

A chuck is sliding downward an inclined plane with friction. The inclined plane has an angel 26 degrees with the horisontal. At a point the chuck has a velocity 4 m/s. The velocity after 2 seconds goes down to 2 m/s. The g is applied to 9.81 m/s^2. So from here I need to find the kinetic and...

1. A 3kg block slides down a rough plane inclined at an angle of 27 degrees. If the acceleration of the block is 2.5 m/s/s find the coefficient of kinetic friction. 2. solving for components Force Net = M x A forces in the y direction: Fn - Fg cos 27 degrees = 0 forces in the x...

1. Problem statement, all variables and given/known data. A 25kg box of books is in the back of the truck. The truck-box system has frictional coefficients (static = 0.4, kinetic = 0.25). You get in the truck and begin to drive in a straight line. Under these conditions a) After reaching your...

Homework Statement A car is moving with a speed of 20m/s when the brakes are applied. The wheels lock (stop spinning). After traveling 40m, the car stops. Determine the coefficient of kinetic friction between the tires and the road. Homework Equations Fk=uk x Fn The Attempt at a...

1. A police officer investigating an accident estimates from the damage done that a moving car hit a stationary car at 25 km/h. If the moving car left skid marks 44 m long, and if the coefficient of kinetic friction is 0.68, what was the initial speed of the moving car? Homework Equations...

Sam, whose mass is 75kg takes off down a 50m high, 10° slope on his jet powered skis. The skis have a thrust of 200N Sam's speed at the bottom of the slope is 40m/s. What is the skis co-effecient of kinetic friction with the ice? Homework Equations Thought originally to use...

Homework Statement A box with a mass of 22 kg is at rest on a ramp inclined at 45 degrees to the horizontal. The coefficients of friction between the box and the ramp are μs = 0.78 and μk = 0.65 a) Determine magnitude of the largest force that can be applied upward, parallel to the ramp...

Consider the system: A block of mass M is placed on a level table and connected to a mass m by a light string running through a pulley. If mass m is released, it will start to fall and the wooden block will be pulled across the table. Prove that the kinetic friction coefficient can be given...

Homework Statement http://img132.imageshack.us/img132/2433/81100769.png Uploaded with ImageShack.us I have a question on part of this problem. Paul accidentally falls off the edge of a glacier as shown in Fig 4-21 (p 103). He is tied by a long rope to Steve, who has a climbing ax. Before...

Ok so I tried making myself a free-body diagram but I reached a dead end.. Step 1) fkinetic = μkn fkinetic = μk(251) fkinetic / 251 = μk Step 2) Fx: T1 Fy n = (m)(g) = 251 N 120.5 N Step 3) ƩFx = m(-a) since it's moving the left or ƩFx = 0 (since it's moving at CONSTANT velocity) ƩFy = ma...

Homework Statement A 20.0g object is placed against the free end of a spring (k = 25.0 N/m) that is compressed 10cm. Once released, the object slides 1.25m across the tabletop and eventually lands 1.60m from the edge of the table on the floor. Is there friction between the object and the...

Homework Statement For our lab we had to find the coefficient of kinetic friction for a cart on a linear track. We pushed the cart on the track and it went through two photogates which measured the time it spent in the photogate. So through the 1st photogate = 0.0040s 2nd photogate = 0.0062s...