When I tutor my physics students, I want them to understand the fundamentals of the concept, not just how to plug in numbers into an equation. I wished when I was learning physics, my teachers drew upon real life applications more, things we already understand about the world to help us really get it.

This article is the second chapter in a series on how to understand and approach kinematics problems. The first chapter covered position, velocity, and acceleration. Now that we understand these quantities, we are going to use them to solve problems in one dimension. 

How to use this guide

This blog post is the first in a series on how to understand and approach kinematics problems. It is meant to supplement your class and textbook. I will focus on practical applications, how to solve problems, and common mistakes that students make. If you want to learn the basics of kinematics, I recommend a textbook, but if you want to gain a deeper understanding, avoid confusion and learn how to approach problems, take the red pill and join us! 

Physics can be intimidating, all those pulleys and protons and projectile motion. If you approach it with the right mindset, however, even the hardest problems are usually easier than you think. When you come up against a tough question, don’t panic. Instead, start with these short, easy tricks to help you work through the problem. 

This week we're spotlighting Yilma, a New York-based Columbia graduate who loves teaching physics, mathematics, and test prepatation! Yilma is currently a Business Associate at a tech consulting firm where she is able to learn about technology and its impact in financial markets. She also occasionally blogs about her experience as a ‘Millennial in Markets’ for the company website.  If you are interested in learning more about Yilma, check out her tutoring profile here.

Intro to Physics Blues   

As a high school student, I took physics my junior year and struggled to stay afloat in the class. While I was interested in understanding and applying the theories I learned, it was difficult to make sense of them in my head. As a result, I began my first collegiate physics course with a lot of excitement, yet some apprehension. 

Learning about logarithms is one of those times in math class where you wonder if this will ever be useful in any way. I see lots of students struggle with topics like logs, since they can seem abstract and they aren’t obviously useful. But I’m here to explain why they are actually incredibly important and describe so much of the world we live in! Let’s take a look at an example from chemistry and physics that shows just how powerful logs can be - the Arrhenius Equation.

Many people, often family members, ask me how astronomy and physics differ. Since I am studying solar physics, I usually give the “short answer”-- that astronomy is just a specific branch of physics. However, there are widespread cultural differences that make the “long answer” rather more involved.

Much like Bill Murray in Groundhog Day, those who take many ETS physics tests may develop a feeling of déjà vu... 

ETS is many things: creative is not one of them. It uses the same questions over and over and over. Therefore, the best way to study for standardized tests of any kind (especially in physics) is to take lots of practice tests. 

Last time on our physics tutoring blog, we conducted an experiment to investigate the influence of the moment of inertia on rolling motion. We started with two objects that had the same shape, but very different size and mass. Starting from rest, we then set them both rolling down a ramp, to see which one would reach the bottom first. The objects had different values for the moment of inertia, but nonetheless reached the finish line at the same time. So, we resolved to try a second experiment, repeating the first experiment but with two objects that have different geometries. Again, to keep it simple, we’ll stay focused on objects that have a circular cross-section, and that are easily found lying around the house. This time, we’ll pit the marble against a roll of masking tape. The roll of tape is larger and heavier than the marble, but from the analysis of our previous experiment we might expect the mass and size not to influence the outcome. Let’s see what happens:

And they’re off! Here is the view from the starting line.

^{And here is a close-up of the finish line.}

We have a winner! The marble beat the tape by a clear margin. So, the geometry of the rolling objects is definitely a deciding factor in this race. Let’s take a look at the math, and compare with the previous experiment. For the roll of tape, we can approximate the shape to be a ring, which has a moment of inertia of I = MR2 when rotated about its center. Using the subscript m to denote the marble and the subscript t to denote the roll of tape, we can set up the energy balance equations in the same way as we did before: