Embedded Files
by Y11 students
This page contains Physics contents discussed in class and re-written by students in prose form to show how well they understood the materials with some elements of creativity and link to the holistic being that the school is promoting through the P.I.A.G.E.T. values. Classmates read the contributions when doing home revisions and/or serve as peer support to others may have fall short of the standard, failed to earned the content-based badges.
Contributions in this page are also part of the 5% PROJECT component of the Final Grade in each term of the school year.
Google Science Journal
Reviewed by Dylan, 23 July 2020
The Science Journal is one of Google's promising applications that shows the good idea of using our phone as a pocket laboratory. I totally agree that we should use it for classroom study. However, it does lack some functionality that makes it a companion to your learning at best.
I will first be addressing its merits. It's a promising idea, using almost all of our phones sensors for detecting things, such as the accelerometer for speed and the light detector for detecting light. However, this app lacks some features, such as finding the area underneath the curve for the graphs, the ability to record data outside of very abstract observations, so it doesn't make the cut for the main tool for home experiments.
I would recommend them adding various functions, such as the ability to differentiate or integrate graphs, finding the gradient of the graph at the exact point, and the ability to plot selected points on a table, so we can make the results more precise, not just base them off of rough estimates. I would also reccomend an app for desktop that can read these .sj files, made by google, so that these observations can be further analysed to obtain more accurate results. Due to the sheer functionality of a personal computer compared to a mobile phone.
I personally do not have a problem with these lack of features, as long as the science journal is used only as a companion to your home experiments, not the main component. This app shows a lot of promise as a revolutionary way to conduct home experiments but it needs some extra functions implemented in order to make it that much better as a tool for our experiments.
The displacement-time Graphs
Tips from Wilbert, 23 July 2020
Displacement-time graph reveals itself as simple if you are already aware of the nature of linear equation and are already having some basic rules in mind. The equation of a line, which normally already elaborated in a Math class prior to your enrolment to a Physics course, provides you with the foundation of knowledge where the concept of displacement-time graph can be anchored on.
Over the years, students have mistakenly switched the displacement and the time because they’re unfamiliar with these phrases or some notations in naming graphs like d-vs-t, s-vs-t, and/or displacement against time. I must note that along the x-axis, time values are plotted. The moment you interchange the axes, magic takes over your interpretations.
The first advice that I can give is to be aware of the units of the displacement and time values to be plotted. I observed that it is common for students to ignore the units given in the question. This almost always lead to errors in the points plotted leading to an incorrect interpretation or answer to the questions asked.
Another important idea to be successful in dealing with this graph is that you should recognize that displacement is a vector quantity, it has a magnitude plus a direction. I assure you all that, with this graph, questions about gradient, which is the velocity, will likely be asked. This is the m we are familiar with in the equation of a line.
To correctly interpret displacement-time graphs, we have to see and understand the positions of the line and how it looks. With these said, here are my tips.
A straight line parallel to the x-axis, see Fig. 1W above, indicates that the object is not moving or at rest because the displacement doesn’t change while time passes. The gradient, as we know, is zero for a line like this.... and this 0 gradient represents a 0 velocity.
A sloping straight line indicates constant velocity, the magnitude of which is equal to the gradient of the line. The direction of this velocity can be deduced from how it goes along the vertical axis. In the case of Fig. 2W above, one interpretaion of direction is that the object is moving away from a given starting point. On the contrary, a downwards sloping line, which cwe can only have when dealing with displacement but not distance, has a a negative gradient which only means that the object is moving backwards or towards a given reference point.
Curved lines mean that the object is either accelerating or decelerating. I am saying this because of the changes in the gradient in curves or equivalently velocity changes. When the gradient is increasing (see Fig. 3W), the object accelerates or moving faster and faster. When the gradient is decreasing as in Fig. 4W, the object slows down.
Simply put, vector addition is the addition of two or more vectors.
Why is this important in the Sciences and engineering subjects? Well, it is because we usually deal with physical quantities with directions, vectors. These directions require us to use specialized method, meaning that we jump to higher level from just the arithmetic of 4 + 3 = 7 since with the inclusion of directions, vectors 4 and 3 when added can give us a certain value between 1 and 7.
You guys must note that there are two main methods to add vectors, namely, graphical methods and analytic methods. When doing the graphs, there are two graphical methods that you can use, one is called Tip-to-Tail and the other is Tail-to-Tail.
Graphical Methods
Tip-to-Tail Method is when the head of the first vector is connected to the tail of the second vector, and to find the resultant vector, a straight line is drawn from the tail of the first vector to the head of the second vector (see Fig. 1A).
The Tail-to-Tail Method is when the first vector and second vector starts from the same point. After drawing the vectors, draw two parallel lines that are parallel to the first and second vectors and a parallelogram will be formed.
To find the resultant vector, or the sum of vectors, graphically, draw a straight line from the tail of the first arrow drawn to the head/tip of the last arrow drawn, in the case of Tip-to-Tail Method (see Fig. 1A again).
If you choose to use Tail-to-Tail Method, on the other hand, you need to use the vectors drawn tail-to-tail and form a parallelogram. Then draw a diagonal line from the initial point where the tails are to the opposite point of the parallelogram (see Fig. 2A).
In any case between the previous paragraphs, measure the line drawn to get the magnitude of the resultant vector. The direction of the resultant can be determined using protractor.
Analytic Method
Analytic method involves the use of sine, cosine and tangent functions, and also the Pythagorean Theorem. In Fig. 3A, a vector is also given the degree, so by using that degree, we can calculate the components along x and along y accurately.
To find out the resultant vector mathematically or analytically,
We use cosine function and sine function to determine the x and y components of each vector.
Then we combine all components determined along x axis. Same with all components along y axis. This way, we can imagine forming a right triangle with sides equal to the sums in x and sums in y.
These sides (or sums) are then to be plugged in to the formula or Pythagorean Theorem to determine the magnitude of the resultant vector.
These sides (or sums) are also used in determining the direction angle through the definition of tangent function.
The formulas in the above 4 steps under Analytic method can be found in Attachment 1A above.
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