 #### Advanced Physics Through Inquiry 1 Teacher Guide

(PS-2848) Teacher guide featuring 15 labs designed for Advanced Placement Physics 1.

### Coefficients of Friction

#### Lab Summary

Students use a motion sensor and a force sensor to determine the static and kinetic friction coefficients between two contacting surfaces.

#### Theory

How can the coefficients of kinetic and static friction between two surfaces be determined? Experimentally determine the static and kinetic friction coefficients between two contacting surfaces.

#### Method

Students use a force sensor to measure the force applied to start an object in motion and drag it across a surface at a constant speed (constant speed is assured by monitoring the velocity of the object using a motion sensor). Assuming the object's speed is constant (net force is zero while the object is stationary and when it is moving), students can assume that the force applied to the object to start it in motion and drag it across the surface is equal and opposite to the frictional force experienced by the object. Using their graphs of applied force versus time, students identify the magnitude of the force corresponding to the static fs and kinetic fk frictional forces and record values for each. In each trial, mass is added to the object, increasing the normal force and thus increasing both frictional forces. Students plot frictional (applied) force versus normal force for both static and kinetic force values. Using the slope of each best fit line, students determine experimental values for the coefficient of static friction and kinetic friction. Combining these two proportionalities, students experimentally derive the equation that summarizes Newton’s Second Law.

#### PASPORT Motion Sensor

(PS-2103A) The PASPORT Motion Sensor accurately measures position, velocity, and acceleration of a target. Can be used to track the motion of carts, balls, people and more.

#### PASPORT High Resolution Force Sensor

(PS-2189) Designed to measure both pulling and pushing forces. Provides a very high resolution of data collection.

#### Discover Friction Accessory

(ME-8574) Four plastic trays with unique surfaces (cork, felt, and 2 plastic) to use with dynamics carts and sensors.

#### PAScar (Set of 2)

(ME-6950) A feature-rich dynamics cart for virtually friction-free motion on a dynamics track.

#### Black Thread (3 pack)

(ME-9875) Black nylon thread.

#### Ohaus Scout SKX Balance 2000g

(SE-8757B) Combines range, resolution and low cost, making it ideal for the student science lab. 2000 g version.

#### Materials Used:

The Ohaus Scout Pro Balance 2000g listed in the Materials and Equipment section is for classroom use, not individual lab stations.

#### Advanced Physics 1 Starter Bundle

(PS-2815) Equipment and sensor starter bundle for performing 8 experiments in the Advanced Physics through Inquiry 1 Teacher Guide.

### Interface Required

This experiment may require software and an interface for data collection.