One of the best strategies for preparing for the Physics 1 exam is knowing what you do not need to memorize.
One of the best strategies for preparing for the Physics 1 exam is knowing what you do not need to memorize. Episode 30 recAPs each unit, with test taking tips, graph reminders and calculator recommendations. Listen for a review of Unit 1 (2:14), 2 (4:01), 3 (6:13), 4 (7:20), 5 (8:28), 6 (9:10), and 7 (9:49)!
Question of the Day (12:13)Asked to find the speed of a 1 kg mass that starts at rest, and is accelerated by a spring, which feature of a force vs position graph could be utilized?
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Hi and welcome to the APsolute RecAP: Physics 1 Edition. Today’s episode will focus on test taking tips and strategies. Specifically, what is worth memorizing or storing on your calculator.
Let’s Zoom out:
Unit – Testing Tips
Topic - 1.1 - 7.4
Big Idea – All
It’s April and you just realized you will be taking one of the toughest examinations of your life thus far (gulp) RELAX! Very few people study effectively in a state of panic. What you don’t need is to stress out or press any big red buttons located nearby. NEVER press the big red button. Everyone knows that! What you do need to do is to take an honest look at a year of Physics 1 content and decide which topics you are weakest on, and which topics you believe you will hit out of the park. That is different for everyone, so you need to do a little soul searching. And… if that doesn’t help, take one of the diagnostic tests in any of the popular review books on the market. Many AP Physics 1 teachers agree that the best one out there is the most current edition of 5 Steps to a 5 by Greg Jacobs.
Let’s Zoom in:
One of the best strategies for preparing for the Physics 1 exam is knowing what you do not need to memorize. You definitely DO NOT need to memorize many formulas, although there are some that can help speed up problem solving and they are not on the published equation sheet. Additionally, most definitions are not worth trying to cram now, but there are some that are definitely worth reviewing. I think the best way to review is to briefly go through each unit and point out the info worth noting. Again, these are the things that should always be swirling around your physics brain.
Unit 1 - Kinematics looked at 1-D and 2-D motion of objects. The most important information worth memorizing in this unit are the graphs of position, velocity, and acceleration versus time. Slope of a position vs time graph is velocity while the slope of a velocity vs time graph is acceleration. The area bound by the acceleration vs time graph is the change in velocity while the area of a velocity vs time graph is change in position or displacement. If you ever forget these, you can simply use your knowledge of their measurement units to determine what the aspects of each graph represent. For example, you are provided with a velocity vs time graph and can’t remember what the slope represents so you realize slope is rise over run and the velocity is measured in m/s on the y-axis, so rise. And the time is measured in seconds and is plotted on the x-axis, so run. Meters per second over seconds is meters per second squared. Voila!
It MAY be worth storing a quadratic formula program in your calculator if you feel comfortable using it to find the time of a moving object. Don’t try and figure it out on the fly during the exam. It isn’t necessary, but can certainly save time especially if you like using it for multiple choice questions. Lastly, know what accelerations means! Like, in your bones! It is a changing of velocity… magnitude OR direction. You can only use kinematic equations for situations where the acceleration is CONSTANT. That means if an object moves with constant speed, and then speeds up. You must treat it as two different problems.
In Unit 2 - Dynamics - the name of the game is practice problems. Do as many as you can, and each time you complete a problem practice the SAME three step process… 1. Draw the FBD and label all forces on the diagram. 2. Sum the forces in both the x and y directions and 3. Set the net force equal to the product of the mass of the object or system and its acceleration. After that 3rd step you can do all of the equation substituting algebra stuff. Force of gravity = mass * little “g” and coefficient of friction is equal to the frictional force divided by the normal force. You will also want to be well versed in the 3rd law. If object A pushes on object B, then Object B will push on object A with equal magnitude and in the opposite direction. Finally, if an object is accelerated, it is because there MUST be a net force. Objects with no net force can still be moving, just not accelerating. Let that one sink in. It is a common area of confusion.
Unit 3 looked at circular motion and gravitation. It is again just forces, so the 3 step process outlined above still works! Just remember that the net force is ALWAYS inwards and can be called the centripetal force. Really, it is just the net force. You should memorize that 2*Pi*radius of a circle divided by the period (time to go around once) is equal to an object’s linear velocity. When looking at orbital bodies then the same 3 step process is again used, just remember that the centripetal force is usually just the gravitational force and if you don’t know little “g” for the location of the object doing the circle, then you need to used the universal law of gravitation equation with big “G”. Orbital speed is just the linear speed of the object, so the circumference over time equation from earlier is also fair game. In other news, you have two equations for gravitational force, so you can set them equal to each other when necessary. This can be super helpful if asked to find little “g” or the gravitational field.
Ahhh Unit 4 - Work and Energy. The most fundamental thing to remember in this unit is that a change in an object or system’s energy is equal to the work done on the object or system. All of the equations are on the formula sheet for this unit, the hard part is knowing when and how to use them. Mechanical energy is all of the potential energy (gravitational and elastic) plus all of the kinetic energy of an object or system. If the mechanical energy is equal at the end of a time interval to what it was in the beginning of the interval then no net work was done and energy was conserved. Energy and work are scalars. Meaning negative energy change means a loss, not in the left or down direction. Therefore, negative work was done on the system. Oo! Oo! I almost forgot, GRAPHS! You absolutely want to know this! A force vs position graph is SUPER useful because the area is equal to the energy change or work done. That can save you a TON of time on multiple choice!
Unit 5 - Momentum. THE conservation law of choice. What you want to memorize here is that a momentum change is equal to the impulse or force times time. If there is not a net external force acting on the system, then the momentum is conserved. That means the system’s momentum at the end of a time interval of a collision for example, is equal to the momentum of the system at the start of the interval. As always… to find momentum change, do final minus initial. You will also want to remember that a graph of force vs time is equal to the momentum change. Again, SUPER helpful as a time saver for multiple choice.
Unit 6 - Simple Harmonic Motion. The unit focuses mostly on simple pendula and spring oscillators. The equations for this unit are again provided. Ultimately, you will want to be able to apply those equations and what you know about energy to most questions on this topic. A graph of force vs position here can be VERY useful since the slope of that graph is the spring constant. You will also notice that for spring oscillators the force vs position graph will also be equal to the energy change for the system or the work done by the spring if the spring’s force is the only one graphed.
Finally, Unit 7 - Torque and Rotational Motion. It’d be good to review information for graphs in the other 6 units just discussed because they still hold true with rotating bodies. The only thing in this unit worth memorizing are the conversions from rotational quantities to linear quantities. It may be worth storing these in your calculator. Angular displacement multiplied by the radius is the arc length or linear displacement in meters. Angular velocity multiplied by the radius is the linear velocity or tangential velocity. Angular acceleration times radius is the linear or tangential acceleration. Those all follow the same pattern, but the weird one is momentum where linear momentum multiplied by the radius is the angular momentum.
There are a ton of equations for rotational quantities, so know how to use them well. The good news is that they are often analogous to the linear concepts from earlier. For example, summing the torques on an object can be set equal to the object’s rotational inertia multiplied by its angular acceleration. Just like Newton’s 2nd Law. And, rotational momentum is conserved unless there is an angular impulse or the product of net torque and the time interval the torques were applied. Finally, the law of conservation of energy is also relevant, and you need to remember that if there is rotation around an axis, then the object has rotational kinetic energy which is also a component of an object or system’s mechanical energy that we now must include.
To Recap…
Obviously Physics 1 is tough, few people sign up for the course thinking it will be easy. But, knowing a few key things before you are presented with the final exam can ease your concerns and help you better manage your time while taking the test. Preparation is the name of the game. Know how to solve problems in a universal way as outlined in this episode, not just how to solve a problem for each specific scenario. The scenarios the exam creators can come up with are literally infinite. And finally, KNOW THE GRAPHS! They will save you a ton of time while testing!
Coming up next on the APsolute RecAP Physics 1 Edition, we continue preparing for the exam and discuss some strategies to think about when taking the multiple choice half of the exam.
Today’s Question of the Day focuses on a test taking tip outlined in this week’s episode.
Question:
Asked to find the speed of a 1 kg mass that starts at rest, and is accelerated by a spring, which feature of a force vs position graph could be utilized?