All Parts of Motion

Position vs. Time graphs, Velocity vs. Time graphs, and Motion Maps.  Anyone know what those are? Anyone?  Well I'm not sure I know either.

This week, we learned about the three things mentioned above, but of course, my mind jumped from certainty to confusion and back again, as I tried to figure out how they worked.  I felt so dumb, especially because I had gone through all of this last year, with the exception of motion maps.  I started off only remembering the names.  Then, there was a flash of light and I instantly remembered what they were, but then I forgot how to draw them.  Then, there was yet another flash of light as I remembered, but now I'm not positive I'm right.

My class seems to be very confused, and that is not boosting my confidence.  Usually, I have a pretty good grasp on what's going on, and I still kinda do.  It's just that we haven't really figured out exactly what they are, and of course our teacher won't tell us.  We have to learn it for ourselves, and I guess that does make sense to some degree.

My First Understandings

This week, we did a lab that dealt with Position vs. Time graphs and Velocity vs. Time graphs.  We were given one of them, and we had to figure out the other.  To do so, we were given a motion sensor and a computer.  We had to try to mimic the graph given, and then draw the other, so if we were given a Position vs. Time graph, we had to do a "walk" in front of the sensor to try to make that graph.  At the same time, the computer would make the other graph, in this case a Velocity vs. Time graph, and we would draw it on our packet.  Then, we would put our "walk" into words, and then draw a Motion Map.

Off of this lab, my understandings were:

• I have no idea how to do a motion map.
• Position vs. Time graphs are easier to do than Velocity vs. Time graphs.
• Your motion sensor is the reference point. (definition in my other post http://ittakesphysics.blogspot.com/2013/10/movin-around.html )
• When you walk towards the motion sensor (reference point), your Position vs. Time graph goes down towards the x-axis, and when you walk away, your Position vs. Time graph goes away from the x-axis.
• If you go at a constant speed, your slope for your Position vs. Time graph is constant.
• If the line is flat on a Position vs. Time graph, your position is constant.
• I seem to only understand Position vs. Time graphs.
• I think I did the lab wrong...

Worksheet Understandings

Then my teacher decided to give us a worksheet called Constant Velocity Particle Model Worksheet 2: Motion Maps and Velocity vs. Time Graphs. Yep, it's a mouthful, but it helped me out greatly.

Off this worksheet, I found out that:

• When an object moves in a negative direction, the velocity is shown as a negative velocity on a Velocity vs. Time graph and when moving in a positive direction, it's the opposite.
• When an object isn't moving, the velocity is 0.
• When an object moves at a steady speed, the velocity is a constant, straight line.
• If the object starts off in one direction at a constant speed and then changes its direction, but still goes at the same constant speed, the graph would look like this:
  
  
• If the object is going the same speed, but in a different direction, the line needs to be at the same number, but negative.
• If the object changes speed, you draw a line straight down because it is changing its velocity instantly.
• This website helped: http://www.physicsclassroom.com/class/1dkin/u1l4b.cfm

Motion Map Understanding

Our teacher then emailed us a reading on motion maps to help us do them on the worksheet. It's http://daisleyphysics.com/worksheets/mmap.pdf 

I learned that:

• Motion maps look like this:

• If an object moves at a constant speed, the arrows have to be the same length.
• To draw one, you must put a point for each time marked.
• The slower the speed, the shorter the arrow, and the faster the speed, the longer the arrow.
• If an object doesn't move, or stays in the same position, you use dots for each amount of time, and since the object doesn't move, the dots stack.
• From the picture above, each notch on the line is a meter.  For the first arrow, it starts at 0 meters.
• If an object turns around, the arrows do too, and they can go over each other because they head back to 0 meters.
• If an object moves in a positive direction, the arrows go to the right, and if the object moves in a negative direction, the arrows go to the left.
• I am still a little confused.

Reflection

This week, I was more confused than I have ever been so far in the year.  However, we still need to have a real, in-depth discussion on it, and I think that will help.  I am doing good in my groups as well, and I am still participating and helping out.  I also feel like I only talk when I need to, at least that's what I try to do.  I am trying not to talk too much, and I am trying not to talk too little.  I guess it's all about making sure I understand, and that is why I have decided to ask questions to clarify certain things that we talk about.