Lab Activity: Determining μs and μk on Different Surfaces

📚 Topic Summary

In this lab activity, we'll explore the concepts of static friction ($μ_s$) and kinetic friction ($μ_k$). Static friction is the force that prevents an object from starting to move, while kinetic friction is the force that opposes the motion of an object already in motion. The coefficients of static and kinetic friction are dimensionless numbers that represent the relative 'stickiness' between two surfaces. We'll determine these coefficients for different surface combinations by measuring the forces required to initiate and maintain motion. Understanding these concepts is crucial in various fields, from engineering design to everyday activities like walking or driving.

The coefficient of static friction ($μ_s$) is defined as the ratio of the maximum static friction force ($F_s$) to the normal force ($F_n$): $\mu_s = \frac{F_s}{F_n}$. The coefficient of kinetic friction ($μ_k$) is defined as the ratio of the kinetic friction force ($F_k$) to the normal force ($F_n$): $\mu_k = \frac{F_k}{F_n}$.

🧪 Part A: Vocabulary

Match the terms with their definitions:

Match the correct letters (A-E) to the numbers (1-5).

✍️ Part B: Fill in the Blanks

Friction is a force that ________ motion between surfaces. ________ friction prevents an object from starting to move, while ________ friction opposes the motion of an object already in motion. The ________ of static friction is typically ________ than the coefficient of kinetic friction.

🤔 Part C: Critical Thinking

Explain how the coefficient of friction might affect the design of a car's braking system. Provide a real-world example.