# What is Static friction: Definition and 505 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.

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2. ### Direction of static friction between a vehicle and circular dome

So the only problem I am having is determining the direction of static friction. I did the same problem but while they were going in a vertical circular motion instead, where the static friction force was in the direction of centripetal force (pointing to the center of the circle). Would it be...
3. ### Static Friction Required to Keep the System from Moving (Two Boxes)

Ok, logically, it must be that the static friction force of block A equal to the force of gravity on block B, so mass of block A is: m_A * 9.8 * 0.30 = m_B * 9.8 m_A * 2.94 = 2 * 9.8 m_A * 2.94 = 19.6 m_A \approx 6.7 kg. However, when I look at block A individually, there is one thing...
4. ### Static Friction Between a Box and the Floor

I don't understand part (b) In part (a), I need to calculate the coefficient of the static friction: mg * \mu_static = 35 58.8 * \mu_static = 35 \mu_static = 35 / 58.8 \approx 0.6 So from part (a) I know that the force applied is equal to the static friction, meaning that the box cannot...
5. ### How do I find the coefficients of static friction and kinetic friction?

I have found that μstatic= 5.6 (found on graph) / 18.20 = 0.3077 I don't know how to find Force of friction from the graph to calculate μKinetic

None yet
7. ### Can't remember equation for coefficient

We did a lab in class on how to calculate it but he collected it and its days later, can't remember how to attempt it.
8. ### B Why is static friction necessary for pure rolling?

Suppose a cylinder is launched on a horizontal frictional surface such that it has initial translational velocity v and zero angular velocity .the kinetic friction would be applied between the contact points of the cylinder and the surface, opposite to the direction of the translational motion...
9. ### B Why doesn't static friction move the other object?

Consider a block sitting on top of a table. When we push the block rightwards, static friction opposes its motion by acting leftwards on the block. By Newton's 3rd Law, static friction should act rightwards on the table. There is now a net rightwards force on the table. Why doesn't the table...
10. ### Static Friction Question — A wood block sliding on a tabletop

I have no idea how to start this other than that I think that Fn is 17.64N and Fnet is 0. But I don't have the mew, so I am not sure how I am going to get the force of static friction.
11. ### B Rolling Motion Test: Take the Challenge and Justify Your Answers

I am posting this to generate a parallel discussion to this ongoing thread. It seems that some participants in that thread have doubts and confusion about rolling motion that might be better addressed separately from the homework problem in question. It is a simple test of one's understanding...
12. ### Force of the wall against the ladder is from static friction?

A ladder is leaning against a frictionless wall and the floor. The force F of the wall against the ladder is what is opposing static friction f at the floor. I don't understand how the force F causes the ladder to slide to the left on the floor unless opposed by friction force f. See picture below.
13. ### I Problem with Static Friction -- Two blocks on a platform

Hello, everyone. This problem is easy if you assume that the friction between the blocks and the platform is the maximum possible. Then the normal force is 0. But how can you show that the normal is 0 even when the friction is less than maximum? Thank you for your help.
14. ### B What Happens When The Applied Force Equals the Static Friction Force?

In my teacher’s notes, it said that when the applied force on an object equals the maximum static frictional force, the object begins to move at constant velocity. My question is if both the applied force and the frictional force cancel as they are equal in magnitude, what force accelerates the...
15. ### Banked curves, coefficient of static friction

The solution in my textbook says that for b, us = 0.234. However when I use the formula above I get 0.2364 which I feel like is too far off. Something must have gone wrong... Any help would be much appreciated! Thanks :)
16. ### I How is static friction the centripetal force during a car turning?

Hello, as you can see i am trying to understand conceptually how the tires during turning create a centripetal force. It was explained to me that as we turn the car tires, the tires similar to a ski or a wedge, now want to push the ground to the side and forward. If the ground was loose, this...
17. ### Static friction coefficient for a crate in the back of a truck

I drew a free body diagram for the crate. I have normal force going up, weight down, static friction force to the left and the force of the crate sliding to the right. I'm assuming the truck is moving to the left. I have Fnet=0 because the crate is not moving, so the forces are balanced. I...
18. ### What determines the direction of static friction forces?

My understanding of static friction is that it is a resistive force in response to an applied force. I recently read the following example. A rope of uniform density, length L, is fastened to a plane with incline angle “theta” along its length. The question asks for the tension at the top of...
19. ### Threshold for static friction

Just wondering, what is the general consensus on the undifferentiable point in a graph of static friction and kinetic friction values regarding whether the object moves or doesn't move? Also wondering what the space between that point and where kinetic friction straightens out is called?
20. ### What happens when a car turns?

A car moving at constant speed is in uniform circular motion, thus having centripetal acceleration of ##a=\frac{v^2}{R}##. The force associated with this acceleration is known to be friction. But friction, in nature, appears as an opposition to the relative motion between two surfaces whether it...
21. ### Static friction — Experiment pulling different blocks across a surface

I know that I am supposed to use the equation I wrote, but how do I find the maximum force of static friction and coeffcient of static friction if none of them are given beforehand? I can't have to unknowns in an equation. We then did the same thing, the only difference was then to measure the...
22. ### Work is not done by static friction when accelerating a car

A recent thread posed the question whether work is done by static friction in the case of an accelerating car. Before I had a chance to reply, the thread was closed on the grounds that the subject was "beaten to death". Undaunted, I am determined to deliver the coup de grâce here with a simple...
23. ### Is there any work done by static friction when accelerating a car?

I'm asking for clarification, but it's my understanding, that of the thread below, and my college physics book Paul A tipler, that when walking or driving a car, the force of friction from the ground does no work. This makes sense in a car becuase the engine/fuel makes the power, driving the...
24. ### Rolling friction and static friction....

Hello, Static friction implies no relative (maybe just instantaneously) motion between the two objects that are in contact. Rolling friction pertains to rolling objects and develops due to the asymmetric deformation of the surface over which the body rolls (if the deformation was symmetric, the...
25. ### Find all forces & the coeff. static friction of a pulley at equilibrium

Given: (block a) m = .500kg (block b) m = .200kg that's all... Fg (block a) = (.5)(9.81) = 4.905N = Fn Fg (block b) = (.2)(9.81) = 1.962N i think acceleration might go like... a = (1.962)/(.5 + .2) = 2.8m/s^2 but isn't it supposed to be at equilibrium? So 0m/s^2. How am I supposed to find...
26. ### Static Friction in Circular Motion

A) So we are given the radius and the coefficient of static friction as 3.0 m and 0.28 respectively. I know that in the vertical direction the only forces acting are the normal force and the gravitational force. Therefore, the normal force is equal to mg because net force is equal to 0, due to...
27. ### Coefficient of static friction and banking of roads

Could you please explain the term 'co-efficient of static friction'? why do the banking of roads or tracks depend of co-efficient of static friction?and not on the co-efficient of kinetic friction?
28. ### Static friction force: Consider a block on a sheet of paper....

Consider a block on a sheet of paper. If the sheet is pulled without sliding the block, who has done work on the block (since it has undergone a kinetic energy variation)? I can not see another force doing work other than the static frictional force on the block.
29. ### Inclined Plane Static Friction Coefficient

Homework Statement The static friction coefficient on an inclined plane is equal to tan(θ). The problem requires me to prove this also works by using an x-axis parallel to the ground rather than parallel to the incline. I understand how to get tan(θ) using the incline as the x-axis, but I don't...
30. ### Motion when Kinetic Friction is more than Static Friction

Homework Statement How would the motion of the block look like when the Force of kinetic friciton is more than the Limiting value of static friction? Homework Equations Kinteic Friciton=μN The Attempt at a Solution I think the block after overcoming the limiting value of static friction will...
31. ### Stopping distance and static friction

Homework Statement A large box of mass M is moving on a horizontal surface at speed v_0. A small box of mass m sits on top of the large box. The coefficients of static and kinetic friction between the two boxes are μs and μk, respectively. Find an expression for the shortest distance dmin in...
32. ### Find min/max accel. for block to stay on wedge (static fric)

This HW problem due date has already passed. I had no problem with part a, but struggled thinking about parts b and c. I saw the solutions for parts b and c, but still don't exactly get it. I'll state the questions below, and tell you my way of interpreting the solution now. Could you tell me...
33. ### Applying Newtons Laws: Incline, static friction, kid on sled

Homework Statement [/B] A child sits on a sled (50kg) on a snowy hill with an incline of 5 degrees. The coefficient of static friction is 0.05. What downward force must a parent apply parallel to the normal force, to prevent the child from sliding down the hill? (Answer: 366N)Homework Equations...
34. ### Force of a Punch to exceed the Max Static Friction Force

I heard that the average professional boxer's force of punch is between 500-750lb. If the coefficient of static friction of rubber (from shoes) to say concrete is at most 0.85 then why can boxers get hit (especially in the chest) without losing footing? Does it have something to do with the...
35. ### Where does static friction come from in ABS?

Ok, so assume we have a wheel on the road traveling to the left. The wheel spins CCW and also has translation to the left. If we let the wheel roll, assuming no slip, then the translation velocity to the left will counteract the rotational velocity to the right at the bottom of the wheel, so...
36. ### Magnitude of the force of static friction

Homework Statement A block of mass M is at rest on an incline that makes angle theta with the horizontal. Given that the static coefficient of friction is mu_s1 and the kinetic coefficient friction mu_k, what is the magnitude of the force of static friction exerted on the block by the incline...
37. ### How Do I Determine Force of Static Friction on a Rolling Car

Homework Statement A 1450-kg car is towing a trailer of mass 454-kg. The force of air resistance on both vehicles is 7471N[backward]. If the acceleration of both vehicles is 0.225m/s^2[forward], what is the force of static friction on the wheels from the ground? Homework Equations Fnet = ma...
38. ### Understanding Static Friction on a Ramp: Why is the Object Stationary?

Hi , The Static Friction force of an object on a ramp(inclined plane) making an angle with the horizontal is greater than the weight component down the ramp. My textbook says that this means that the object on the ramp is stationary as the frictional force is greater than the weight component...
39. ### Static friction confusion -- Friction versus the Normal force

I am a bit confused. We have an inclined plane. So I know that Ffmax=μ*N and μ is the coefficient of friction calculated as tgθ (θ is the angle at which the body is on the verge of sliding) and also Ff<=Ffmax And we know that the force that makes the body slide is mgsinθ. So as the angle...
40. ### Static friction rotating an object

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...
41. ### Static friction and a rotating object

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...
42. ### How do i find the coefficient of static friction?

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...
43. ### Torque to Overcome Static Friction of a Rolling Object

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...
44. ### Acceleration of object with friction: Homework help

A 50 kg box rests on the floor. The coefficients of static and kinetic friction are 0.70 and 0.50, respectively. a.) What is the minimum force required to start the box sliding from rest? b.) After the box starts sliding, the person continues to maintain that force. What is the...
45. ### Is Static Friction Capable of Doing Work?

I understand the whole explanation about why static friction does no work-- I'm just confused about one of the consequences of that. Consider the picture above. The ring is being pulled down the incline with a force of mg*sin(θ). If you analyze the system about the axis at the center of mass of...
46. J

### Static Friction carnival ride Problem

Homework Statement In a classic carnival ride, patrons stand against the wall in a cylindrically shaped room. Once the room gets spinning fast enough, the floor drops from the bottom of the room! Friction between the walls of the room and the people on the ride make them the “stick” to the wall...
47. ### Is the Work Done by Static Friction Always Zero in a Round Trip?

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...
48. ### Static friction force homework

Homework Statement A 50kg object begins at rest on a surface with a static coef of friction at 0.6. If you push horizontally on the object with a force of 27N, how quickly will it move across the surface? Homework Equations The Attempt at a Solution[/B] This is from Trivium Praxis test prep...
49. ### Car on a hill - reasoning for static friction

Problem : A car of mass ##m## is parked on a slope. What does static friction ##\mu_s## have to be for the car not to slide down if the incline of the hill is ##30## degrees? ******* For this problem I have the following forces, where the hill is inclined upwards to the right: Upwards ...
50. ### Contact force of block on a wall

Homework Statement In this sketch, the mass m = 1.6 kg is pushed against a wall by force F, as shown, in the horizontal direction. The values of the coefficients of kinetic and static friction for the contact between are 0.81 and 0.84 respectively. The magnitude of F is slowly and continuously...