Question

What is the difference between non-contact and sliding friction? What are some examples of each? What factors affect friction (e.g., load, speed, lubrication)?

Answer 1

Non-contact friction, also known as air resistance or fluid resistance, refers to the resistance encountered by an object moving through a fluid medium, such as air or water. It arises due to the interaction between the object's surface and the molecules in the fluid. Sliding friction, on the other hand, is the force that opposes the motion of an object sliding or moving across a solid surface.

Examples of non-contact friction include:

1. Air resistance acting on a moving car, cyclist, or airplane.
2. Water resistance experienced by a swimmer or a boat moving through water.

Examples of sliding friction include:

1. The resistance experienced when pushing a heavy object across a floor.
2. The friction between the wheels of a car and the road surface.
3. The friction between the soles of shoes and the ground while walking.

Factors affecting friction include:

1. Load or Normal Force: The force exerted by an object on a surface affects the frictional force. Greater load or normal force increases the frictional force.
2. Surface Roughness: The roughness of the surfaces in contact influences the frictional force. Rougher surfaces tend to have higher friction.
3. Coefficient of Friction: The nature of the materials in contact determines the coefficient of friction, which quantifies the frictional force. Different materials have different coefficients of friction.
4. Lubrication: The presence of a lubricant, such as oil or grease, between two surfaces reduces friction by providing a smoother interface.
5. Speed: In some cases, the speed of relative motion between the surfaces can affect friction. For example, the frictional force between tires and the road surface can change with speed.
6. Temperature: Frictional properties can be influenced by temperature. For instance, lubricants may become less effective at higher temperatures, leading to increased friction.
7. Surface Area: The area of contact between two surfaces can affect friction. Greater surface area can result in higher frictional forces.

It's important to note that these factors can interact with each other, and the overall effect on friction can vary depending on the specific circumstances.