Relative Motion

This week in physics we learned about relative motion.  We already knew that all motion is relative, meaning when observing the motion of something; we must ask ourselves what it is moving relative to. Relative motion is the calculation of the motion of an object with regard to some other moving object. When calculating the velocity of the motion of an object, we do not measure the velocity relative to the ground, but to another moving object.

The picture below is of my friend Kainalu at ILH Champs Cross Country race last week. Lets say for example he and the Punahou guy right behind him are both running at 10mph. If this were the case, they would both not be moving relative to each other. However, if Kainalu were to accelerate to 12mph, relative to the other runner, he would be moving away. Also, relative to Kainalu, the other runner would be moving backwards, even though he is remaining at the same speed. Relative to the other runner, Kainalu would be running at +2mph. Relative to Kainalu, the other runner would be running at -2mph. 

Projectile Motion

This week in class we have been learning about projectiles and projectile motion. Projectile motion is an example of 2D kinematics. This means that there is motion happening on two different axes. There is motion happening on both the x, and y-axis in 2D kinematics. Projectile motion follows the “Vegas” rule, which means what happens on a certain axis, stays on that axis. I was bored this Sunday and was throwing cashews (I’m nutty for cashews. So punny) off my apartment balcony. I saw that these cashews became projectiles. They were accelerating down towards the ground at 9.8m/s² and were moving forward with the velocity at which I threw them. Having movement on two different axes made these cashews projectiles.

Vectors

In this unit of physics, we have been discussing vectors. A vector is a quantity that has both direction and magnitude. Magnitude pretty much means amount of something. So a vector quantity is described by its amount and the direction of that amount. Some vector quantities are velocity and acceleration. Velocity is a vector quantity because it involves a speed along with a direction in which the object is moving. Acceleration is a vector quantity because that same object can be increasing or decreasing velocity in the same or a different direction. The picture below is of me skating down a ramp in the parking lot. This relates to vectors, because I am accelerating at a certain rate in the direction of the lower level. 

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Final Quarter Blog

We have learned a lot in this first quarter of physics. We began by reviewing some simple science concepts, like accuracy vs. precision. Accuracy is how close you are to the actual value, and precision is how repeatable your values are. We focused a lot on kinematics, the branch of physics concerned with motion, this quarter. All motion is relative, so when questioning if something is moving, you must ask “relative to what?” If I was running with someone at the same speed, relative to the ground we are moving, but relative to each other, we are not moving. We also learned about velocity, which is the speed of something in a given direction. To calculate average speed or velocity, you take the total distance traveled divided by the total time. We also learned about acceleration, which is the increase in the rate of speed of something. Acceleration is equal to change in velocity divided by change in time. We learned many useful equations on the “EQUATION BOARD, NOT BORED.” One of the important equations we learned that distance=(velocity)(time). This equation can be used to find the distance, velocity, or time of motion of an object depending on what givens are given. The picture below is me dropping my eraser. Since I am on earth, the eraser will have an acceleration of 9.8m/s^2 down. This means that my eraser is increasing in speed the longer it is in free fall.