Example 1: General Physics
1. What did I learn during Week #?
Physics consists of several major topics of which include: mechanics, heat (molecular physics), electricity, optics and atomic and nuclear physics. So far, we have started covering mechanics, the study of motion or the change of a position of an object with respect to another motion. When we speak of motion we should follow two models: one regarding dimensionless objects and the other regarding reference frames.
Dimensionless objects are objects whose size are less then the distance they covered. The second model states that we always need a frame of reference, For example, it would be silly to say a person sitting down is not moving. The reason for this is that the person is really moving in reference to perhaps an astronaut standing on the moon since he/she is standing on Earth, which is continuously moving. However, the person sitting down is not moving in reference to the ground. Therefore, we should always mention in reference to what we're talking about, in other words, a reference frame.
We are currently studying kinematics, a branch of mechanics that describes how objects move. Its goal is to predict the position of an object. How can we describe motion? We can describe it by using measures such as velocity and acceleration. Velocity, a vector quality, is displacement, a vector representing the shortest distance from the initial to the final position of a motion, over a certain time (). Acceleration, on the other hand, is a vector that represents the change in velocity over a certain period of time (). We can also measure the velocity and acceleration t a particular instant of time. These are called the instantaneous velocity and instantaneous acceleration. Instantaneous velocity is defined as the change in displacement over time as the limit of the change in time approaches zero. Instantaneous acceleration is defined as the change in velocity over time, as the change in time approaches zero. In class, we also learned that at constant velocity, displacement is proportional to time, and at constant acceleration, velocity is proportional to time.
The final topic we covered was free-fall. A free-falling object is any object that accelerates up or down under the influence of gravity. Free fall is represented by g, whose magnitude is equal to 9.8 m/s2. Free-fall is just a model since it doesn't really exist on Earth. It could only exist if there were no air resistance, which Earth of course lack.
Here are the important equations we learned:
Average velocity: |
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Average acceleration: |
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Instantaneous velocity: |
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Instantaneous acceleration: |
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At constant velocity: |
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At constant acceleration: |
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