Physics 12/14

Speed is a scalar quantity, using a numerical value and units to describe how fast an object is moving. Velocity is a vector quantity, using a numerical value, units and direction to describe how fast an object is moving and in what direction it is moving. Speed could be 75 km/hr, 61 mph, or 3 m/s. Velocity would look like 32 m/s North, 8 ft North, or 6 mph SW. Velocity is important. If someone told you that you had to go 7 meters at 1 m/s to get to the bathroom, you could go in as many directions as you wanted to and you would have a very low chance of ever reaching the bathroom. if someone told you that you had to go 7 meters to the left at 1 m/s, you would be able to find the bathroom right away. To show the relationship between the position of an object and time, we use position v. time graphs. Position v. time graphs show where an object is and the time it took to travel there. On the graph, the horizontal axis is time, and the vertical axis is position. If the line on the graph is horizontal, that means that the object is not moving. If the line is vertical or sloped, the object is moving at a steady speed.

Image by Mariana Garcia-Serrato/GoFormative

The first part of the line shows that the object is moving at a steady speed and that time is passing. The line cannot end halfway through the graph because that means that time has stopped, and that can't actually happen (yet). The horizontal part of the line shows that the object has stopped moving and is stationary. Then the third part of the line is more sloped than the first, meaning that the object has picked up speed and is moving after. 

S&EP: SP4 Analyzing Data

This week, we analyzed data in tables to match different graphs, tables and stories together. Different graphs can have different stories that go with them. For example, the graph above can have a story like this: Jerry started out on his walk to school. His watch fell off of his wrist, and he stopped for a while to look for it. When he found it, he started to run because he was going to be late for school. This story matches the graph, because the object/person started out slowly (walking) and then stopped (looking for the watch), then picked up speed (running because he was late). Using graphs can help find the average speed for different objects. On Friday in class, we built a Hot Wheels course and ran four different cars down it. We measure the distance the cars moved and how long it took them to move that far, and then we calculated their average speeds to see which was fastest. 

XCC: Cause and Effect

In the example of the hot wheels course, cause and effects can matter a lot. When measuring the speed and velocity of the cars and comparing them to see which is the fastest, it's important to keep the course the same. If a green car ran one course, and a black car ran a steeper course, then the experiment wouldn't be fair. Both of the cars need to run the same course for the experiment to be fair. A steeper course could make the car go faster, and a flatter course might let it go slower. Even if both cars were on an unchanged course, an accidental push of one of the cars could let it go faster or move further than it would've on its own.