TL;DR If you want a quick way to gauge whether or not students understand the concept of potential energy, you can ask them to explain the origin of The World’s Most Annoying Negative Sign. It is merely a consequence of the very definition of potential energy, which is almost never explained coherently. In all of […]
Read More The World’s Most Annoying Negative SignTL;DR In this pandemic year, cheating has been a major concern. One way of mitigating its effect is to ask questions beyond the traditional “Calculate…” type of physics problem. I present a list of possible questions that can’t be easily searched online and even if they’re found the answers are not as likely to be […]
Read More Different Test or Assessment QuestionsThis question is particularly revealing in that it assesses whether or not students understand the coordinate-free nature of work as a dot product. Be prepared to hear such nonsense locutions as “negative force” or “negative displacement” but don’t be shocked when you hear them. I think it’s a product of the relatively poor treatment vectors […]
Read More Conceptual Understanding in Introductory Physics XXXVI: Geometry and WorkFree-body diagrams are ubiquitous in introductory physics courses. They should be straightforward, but I’ve noticed that student frequently struggle with them at first because they want to include velocity or momentum in addition to forces. For this question, choose an arbitrary (the more arbitrary, the better) physical situation. It could be something from your or […]
Read More Conceptual Understanding in Introductory Physics XXXV: Free-body DiagramsDraw an arrow representing an arbitrary force vector and another arrow representing an arbitrary momentum arrow. Label both arrows. Ask the student to perform the following task: Decompose the force vector into a component parallel to the momentum vector and a component perpendicular to the force vector. Tell whether or not the given force will […]
Read More Conceptual Understanding in Introductory Physics XXXIV: Parallel and Perpendicular Components of ForceThe instructor draw a random diagram showing an arbitrary number of interacting (e.g. gravitationally) entities (e.g. stars, asteroids, etc.) represented as numbered dots. The student is asked to perform the following tasks: Draw a system boundary such that the system experiences a net external force. Name each entity that contributes to this net external force. […]
Read More Conceptual Understanding in Introductory Physics XXXIII: Drawing SystemsThis question is a numerical version of the previous question. For a given arbitrary vector quantity , calculate the following quantities. Use a different vector quantity for each student, and have them do the calculations in a programming language in real time (like GlowScript) to demonstrate coding proficiency. Additionally, these calculations can be done very […]
Read More Conceptual Understanding in Introductory Physics XXXII: Practice With Simple Vector ComptuationThis is the first in a series of sample questions I’ve used in oral interviews.
Read More Conceptual Understanding in Introductory Physics XXXI: Practice With Vector NotationI just realized this is the thirtieth post in this series! I don’t know if anyone has found this series helpful, but I think these questions collectively might make a pool of original exam questions. That’s mainly how I see them anyway. This post is almost a word for word duplicate of the last post […]
Read More Conceptual Understanding in Introductory Physics XXX: Two Expressions for the Cross ProductStudents sometimes see vector dot products in their calculus classes before they see them in their physics classes. Dot products are often presented with two seemingly unrelated definitions, one of which is geometric and coordinate free and the other is in terms of components in a particular basis. Yet, the two give exactly the same […]
Read More Conceptual Understanding in Introductory Physics XXIX: Two Expressions for the Dot Product