MET 2400 - Chapter 6; Friction

What is friction?

Friction is a retarding force that resists the relative movement of two bodies in contact, acting opposite to the direction of motion.

What is the coefficient of static friction (μs)?

The coefficient of static friction (μs) is the ratio of the maximum available frictional resistance (F) to the normal force (N) between contacting surfaces: μs = F/N.

What factors influence the coefficient of static friction?

The coefficient of static friction depends primarily on the type of materials and the nature of the contacting surfaces.

How is the frictional force related to the normal force?

The frictional force (F) is proportional to the normal force (N), expressed as F = μ(Sub s)*N.

What is the angle of static friction (Φs)?

The angle of static friction (Φs) is defined by the relationship tan(Φs) = F/N = μs.

What is the first step in solving motion-impending friction problems?

Draw the free-body diagrams showing all applicable forces and determine the direction of impending motion.

What equations are applied when forces are concurrent in friction problems?

Apply the equations of force equilibrium: ΣFy = 0 and ΣFx = 0, along with F = μsN.

What additional equation is used when forces are not concurrent?

In addition to the force equilibrium equations, apply the equation of moment equilibrium: ΣM = 0.

How do you calculate the force P required to cause motion to impend?

Use the equations of equilibrium to solve for P, considering the weight and frictional forces acting on the body.

What is the significance of an inclined plane in friction problems?

An inclined plane assists in moving heavy objects, and the angle of the incline affects the forces acting on the object.

How do you find the weight of an object on an inclined plane?

The weight (W) can be calculated using W = mg, where m is the mass and g is the acceleration due to gravity.

What is the role of the normal force (N) on an inclined plane?

The normal force (N) acts perpendicular to the contact surface and is essential in calculating frictional forces.

How do you determine the direction of the resisting friction force?

The resisting friction force acts opposite to the direction of the impending motion of the body.

What is the relationship between the forces acting on a ladder supported by a wall and floor?

The forces include the weight of the ladder, the weight of any person on it, the normal forces at the wall and floor, and the frictional forces.

How do you calculate the horizontal and vertical reactions at points of support for a ladder?

Use the equations of force equilibrium for both vertical and horizontal forces to solve for the reactions at the support points.

What is the maximum angle of static friction?

The maximum angle of static friction occurs when motion is impending, and it can be calculated using the relationship tan(Φs) = μs.

What happens when the applied force P exceeds the maximum frictional force?

If P exceeds the maximum frictional force, the object will begin to slide in the direction of the applied force.

What is the significance of the coefficient of friction in practical applications?

The coefficient of friction is crucial for determining how much force is needed to initiate or maintain motion between surfaces.

What is the formula for calculating the frictional force when the coefficient of static friction is known?

Frictional force can be calculated using F = μsN, where N is the normal force.

How does the angle of the incline affect the normal force?

As the angle of incline increases, the normal force decreases, affecting the frictional force available.

What is the effect of increasing the weight of an object on friction?

Increasing the weight of an object increases the normal force, which in turn increases the maximum frictional force.

How can you determine if a body will slide down an inclined plane?

Compare the component of the weight acting down the incline with the maximum frictional force; if the weight component exceeds it, the body will slide.

What is the relationship between the angle of the incline and the forces acting on a body?

The angle of the incline affects the distribution of forces, including weight components and normal force, influencing motion and friction.