Today we will be looking at the energy unit test, then continuing to work on momentum and collisions.
Momentum test on Friday.
1/30 AP Phys: Energy Multiple choice practice problems
Today’s assignment is a set of multiple choice problems. The answers are below:
- D
- A
- C
- A
- D
- A
- B
- B
- A
- D
- A
- A
- A
- C
- D
- A
- C
- D
- B
1/29: Review for Friday’s test on energy
Please post any questions you have in the comments section below. Remember to designate which worksheet/page/etc. the problem is from.
1/28: AP Phys: Power
In our study of energy and work, we have yet to address the time it takes to transfer energy from one system to another. This rate is called power, and given symbol P (upper case, we’ll use the lower-case p for another variable later). Since the rate is time based, the equation for power is:
P = Δ E/ Δ t
The units for power from this equation would be J/s, which physicists shortened to Watt, with the symbol W (upper-case since it’s named after a person, James Watt). So…
1 J / s = 1 W
Class practice
Work your way through Problem 5.12 on Page 143.
Class and homework
Page 154, problems 48, 50, 51, 53, 54
Book resources
Section 5.6: Power, pages 142-146
Some power trivia
- The most powerful production car (not specially built or modified) is the Bugatti’s 8.0-litre W16 in the Chiron. Four turbos help this car mill 1,479hp (1.2MW) through its 8.0-litre quad-turbo W16 engine, producing a massive 187.5 horsepower per liter. It’s mass is 2,000 kg.
- The most powerful pickup truck is the 2019 Ford Super Duty (F250 and F350). Ford’s 6.7-liter diesel V8 delivers 450 horsepower (336 kW); more than any other truck in this class. The mass of this truck is 3,500 kg.
1/27 AP Phys: The Rope Swing
We went over some of the problems from last week.
Continue reading “1/27 AP Phys: The Rope Swing”1/23-24 AP Phys: Energy practice problems in your textbook
Homework/classwork
Thursday
Page 152, Problems 21-24
Friday
Page 153, Problems 33, 35 (both spring energy), 47 (a red, make sure to do drawings before you start!), 29, 30, 32, 34, 43
Jackson suggests you do Problems 73 and 75; I guess I’ll have to try these this weekend 🙂
Questions? Post them below. Don’t forget, you can log in with just about any social network and receive email updates when your question is answered.
1/23 AP Phys: Quantifying spring energy
Write the slope of your F/x calculations for each spring under the matching color on the whiteboard on the right.
Spring constants
As we saw yesterday, the relationship between the force applied to a spring and the stretch of the spring is linear. The slope of the F/ Δ x plot is
F = k* Δ x
which can be rearranged for the spring constant:
k=F/ Δ x
and the units of the spring constant must be N/m.
Review: Video showing the calculation of a spring constant
Similar to the lab we did in class, only this one uses the force of gravity between the earth and a hanging mass.
Calculating the energy in a spring
We demonstrated this both with algebra/geometry and with integrals in calculus. Vide of this will appear below soon.
Calculation video will appear here soon.
Flipping physics video.
Class/homework
In your textbook, Page 152, Problems 21-25. Complete tonight so we can whiteboard them tomorrow.
Problem 22: Here is a video of helper springs at work: https://youtu.be/GQs79EIw81M (this video is set to not allow embedding in other web sites. Below is another video that did allow embedding.
1/22 AP Phys: Energy in springs: Hooke’s Law and Spring constants
Goals
- Analyze the relationship between how far a spring is stretched (Δx) and the force required to hold it at that distance.
- Develop a model for energy in a spring based on (ΣE) + W = (ΣE)
- If the spring has no initial energy, then the work done on the spring equals the final elastic/spring energy.
Procedures, general outline
You will need to think about how you are making the following measurements, and record the details of your procedures in your lab book.
- Before you start, read the procedures and create a data table with all the necessary columns and rows.
- Chose a tubular spring scale from the bin, and records its color.
- Pull a spring scale out and hold it at any distance.
- Record the stretch (Δx) of the spring.
- Record the force measurement of the scale.
- Repeat at several different lengths, until you are comfortable that you can plot the data and be confident that your choice of linear or exponential fit is an accurate model.
- Repeat steps 2-6 for a total of three different colored spring scales.
Analysis
- Analyze your data using a scatter plot, and develop an equation for each spring.
- Plot stretch as the independent variable.
Conclusion development
- Develop conclusions with your group about the relationship.
- Prepare to present a whiteboard tomorrow: You should have a small box in your lab book showing what you will write on your whiteboard tomorrow.
1/15 AP Phys: Conservation of energy with springs & ramps
Learning objectives
The student is able to describe and make qualitative and/or quantitative predictions about everyday examples of systems with internal potential energy. (Science Practices 2.2, 6.4, and 7.2)
Introduction
Observe the demonstration and take notes on your observations and questions. Think about/answer the following questions:
- If the track were steeper or shallower, how would the motion change? Justify your answer using your knowledge of kinematics and energy.
- Short answer on our own (2 minutes).
- Expand answer with our group (3 minutes) .
- Expand answer with the class (5 minutes) .
Equipment
- Low friction cart
- Ramp
- Meterstick
- Stopwatch
- Assorted masses
Tools
- Calculator
- Clinometer to measure angle of ramp
- Whiteboard for sharing group work
- Books or other objects to change the steepness of the track
Safety
- Please keep carts on tables to prevent people from slipping on them (or damaging them).
- The carts have spring plungers; make sure they aren’t compressed near delicate parts of your body, or breakable objects.
- Think and be careful
Design and conduct an experiment to answer the following question.
- If the track were steeper or shallower, how would the motion change? Justify your answer using your knowledge of kinematics and energy.
Keep focused on your objective!
Provide detailed procedural steps. Make sure that if you gave them to someone who had not completed the lab, they could do everything completely and in the same way your group did it.
Why are you doing each step, and what are reasonable measurements.
Are you completing these steps as you progress?
- Prelab notes
- Title
- Purpose
- Personal procedures/ideas
- Group procedures/ideas/notes
- Class procedures/ideas/notes
- Data table
- Notes on experiment from as you conduct it.
- Scatter plot or other visual analysis of data.
- Processing/analyzing data:
- Group conclusion (what can your group conclude, without looking at other groups’ data?)
- Whiteboard notes
- Class data comparison and conclusions.
01/8-13 AP Physic: Energy
Wednesday & Thursday, Jan 8 & 9
We added energy equations and the work work/energy theorem to our energy knowledge. In physics, work is used to add or remove energy from a system.
Class/homework: Page 151, # 9-18
Friday, Jan 10
We worked on an energy simulation using the PhET Energy Skate Park simulation. You can see the assignment here, and the simulation here:
Monday, Jan 13
We started learning about power. Textbook Section 5.6, pages are 142-146. Solve problems 48-54 on page 154.