Introduction: Free-body diagrams and friction
The basis of what we cover in 1A03 has been understood for hundreds of years. These fundamental physics laws, while not new, are still highly relevant and applied daily in new and exciting ways to help us further our understanding of the world around us. While this particular lab focuses on the groundbreaking work of Sir Isaac Newton, it’s important to remember that our current understanding of physics is a result of the combined efforts of a large diverse group of scientists. And by performing these labs, on your own, you are all now gearing up to contribute to the vast data and understanding of our universe, you are training to become scientists (fight imposter syndrome!). A big part of the understanding process has been developing tools like mathematical notation and free-body diagrams. In this lab you will use these tools to understand the forces in your experiments.
Newton’s Laws, the way Newton wrote them. With free-body diagrams and mathematical notation, you will be able to explain the second law much more clearly.
In Exercise 1, you will use a free-body diagram to make some predictions about the experiments to follow. You will see how the forces in the following experiments should balance, and develop some equations of motion for your experiments that you will test in the following exercises.
Exercise 2 has you measuring the force of static friction between your shoe and an inclined smooth surface. By measuring the angle of the inclined surface where the shoe just begins to slip, you will be able to quantify the coefficient of static friction between your shoe and the flat surface (i.e. measure the mu of a shoe).
Likewise, in Exercise 3 you will be measuring another friction coefficient; but this time you will be looking at kinetic friction. Similar to Exercise 2, you put your shoe on an inclined surface that is slightly steeper. The shoe will accelerate down the ramp; you can determine the acceleration by timing how long it takes to slide and by measuring the length of the ramp. Once you know the acceleration of your shoe, you can calculate the coefficient of kinetic friction.
In Exercise 4 you will interpret and draw a graph of force of friction as a function of the applied force. This will lead into a final discussion question in Exercise 5 that will test your understanding of all these concepts.
Learning Objectives
Set yourself the following learning outcomes for this lab:
By the end of this lab, I will be able to
- Analyse physical situations, and draw representative Free Body Diagrams for both stationary and in-motion scenarios.
- Write equations that describe the force of friction in a given situation (both static and kinetic friction).
- Apply the concepts of friction to real-life scenarios.
- Identify static vs. kinetic frictional forces and how they affect motion.
But before any of that, it’s important to get warmed up!
