I created this post here to bookmark some useful tools for use during my upcoming JC1 lectures on Dynamics.
This is a simulation for collisions that show the momenta before and after collisions. It requires registration after one visit.
A better choice for now could be the EJSS version (created by my ex-colleague Lawrence) which is far more detailed.
I had wanted to build one using GeoGebra and in fact, was halfway through it, but the Covid-19 pandemic has created other areas of work that now take priority.
Problems involving two bodies moving together usually involve asking for the magnitude of the force between the two.
For example:
A 1.0 kg and a 2.0 kg box are touching each other. A 12 N horizontal force is applied to the 2.0 kg box in order to accelerate both boxes across the floor. Ignoring friction, determine:
(a) the acceleration of the boxes, and
(b) the force acting between the boxes.
To solve for (b) requires an understanding that the free-body diagram of the 1.0 kg box can be considered independently as only the force acting between the two boxes contributes to its acceleration since it is the only force acting on it in the horizontal direction.
This interactive app allows for students to visualise the forces acting on the boxes separately as well as a single system.
The codes for embedding into SLS:
<iframe scrolling="no" title="Two Mass Problem" src="https://www.geogebra.org/material/iframe/id/fh5pwc37/width/638/height/478/border/888888/sfsb/true/smb/false/stb/false/stbh/false/ai/false/asb/false/sri/false/rc/false/ld/false/sdz/false/ctl/false" width="638px" height="478px" style="border:0px;"> </iframe>
In a recent class on Kinematics, I prepared a string of 4 pendulum balls, each separated about 20 cm apart and dropped them from a height. Before that, I got students to predict whether the intervals in time between drops will be constant, increasing or decreasing.
Most students are able to predict rightly that the intervals will be decreasing and explain their reasoning.
What challenged me was this: previously, we had to listen to the intervals of sound to verify the answer. I had tried using laptop software such as Audacity to record the sound before. However, I wanted students to be involved in this verification process. PhyPhox enabled that.
With each student being able to download the mobile app into their phones, all I needed to do was to ensure everyone uses the correct setting: the Audio Scope setting and to change their range to the maximum duration (500 ms). They then had to be familiar with the play and pause button so they can stop the measurement in time to see the waveform.
I then did a countdown before dropping the balls. This is an example of the graph obtained.
Through this graph, you can see that:
the time interval between drops decreases as the balls dropping over a larger height had gained more velocity by the time they reach the table.
the amplitude of sound increases as the balls drop with increasing velocity, therefore hitting the table with larger force.
Through this GeoGebra app, students can observe how the gradient of the displacement-time graph gives the instantaneous velocity and how the area under the velocity-time graph gives the change in displacement.
In the GeoGebra app below, you will see a displacement-time graph on the left and its corresponding velocity-time graph on the right. These graphs will be referring to the same motion occuring in a straight line. Instructions
Click “Play” and observe the values of displacement and velocity change in each graph over time.
Note the relationship between the gradient in the displacement-time graph and the value of velocity.
Note the relationship between the area under the velocity-time graph and the value of displacement.
This GeoGebra app allows users to change the magnitude and direction of the force acting on an object, as well as the initial velocity.
The change in kinetic energy is calculated along with the work done in the direction of the force.
This demonstrates a very important concept in Physics known as the Work-Energy Theorem, where the net work done on a particle equals to its change in kinetic energy.
