Law Of Motion || Types Of Friction || Lecture No. 18

Summary

In this video, the speaker explores the concept of friction, highlighting its two main types: static and kinetic friction. Static friction is further divided into self-adjusting and limiting friction, while kinetic friction includes sliding and rolling friction. The video emphasizes that limiting friction, determined by the normal reaction force, is independent of the contact area, contrasting with general frictional force, which varies with area. Through practical examples and graphical representations, viewers gain insights into how applied forces interact with friction, culminating in an understanding of the dynamic nature of these forces in real-world scenarios.

Takeaways

• 😀 There are two major types of friction: static friction and kinetic friction.
• 🤔 Static friction has two subtypes: self-adjusting friction and limiting friction.
• 🏋️‍♂️ Kinetic friction can be categorized into sliding friction and rolling friction.
• 📉 The highest friction occurs with static friction, followed by sliding friction, and the least is with rolling friction.
• 📐 The limiting friction force is directly proportional to the normal reaction force.
• 🔄 The value of the coefficient of friction depends on the surface in contact and has no units.
• 🛑 Limiting friction force is independent of contact area, while friction generally depends on it.
• 🧩 The nature of the contact surface changes the limiting friction value.
• 🔄 An example is given where a 50 kg block in square and rectangular shapes is discussed regarding which has more limiting friction.
• ⚖️ When an applied force is less than the maximum limiting friction, the friction force equals the applied force.

Q & A

What are the two major types of friction mentioned in the video?

The two major types of friction are static friction and kinetic friction.

What are the subtypes of static friction?

Static friction has two subtypes: self-adjusting friction and limiting friction.

What are the subtypes of kinetic friction?

Kinetic friction has two subtypes: sliding friction and rolling friction.

Which type of friction is the highest, and which is the lowest?

Static friction is the highest, followed by sliding friction, while rolling friction has the least amount of friction.

What does limiting friction depend on?

Limiting friction is directly proportional to the normal reaction force; the greater the normal reaction, the greater the limiting friction force.

How does the nature of the surface in contact affect limiting friction?

The value of limiting friction changes based on the nature of the surface in contact. For example, different surfaces will have different coefficients of friction, affecting the limiting friction value.

In the example provided, which shape between a square and a rectangle has higher limiting friction?

In the case of equal mass (50 kg for both), the limiting friction force will be the same for both shapes since the normal reaction force is the same.

What is the maximum value of friction as discussed in the video?

The maximum value of friction, or limiting friction, represents the maximum force of friction that can be generated before motion occurs.

What happens to the friction force when the applied force is less than the maximum friction?

If the applied force is less than the maximum limiting friction, the friction force will equal the applied force, not the maximum value of friction.

What is the relationship between applied force and friction force in the graph described?

The relationship is linear up to the maximum value of limiting friction. Once the applied force exceeds this limit, the object will start moving, and the friction will transition to kinetic friction, which remains constant.