Student "edition" found at {csi dot journalspace dot com}.

Maybe I shouldn't have started this blog now, not with everything that's been going on.

In the second meeting of my mechanics lecture students for the seventh week of classes for the second term of the school year, I started the discussion on two dimensional motion based on a given initial velocity and direction, otherwise known as Projectile Motion.

Of course the first part of this was to get the component velocity of the resultant along the vertical and along the horizontal.

Then I had to emphasize for them, since it was already one of the questions in their experiment about the topic at the start of the week, that horizontal motion is governed by constant velocity while vertical motion is governed by constant acceleration (or free fall) but simultaneously, which is why only time is the quantity that can be used for both cases. I made them recall that for constant velocity, we only have to deal with one equation, and still the five equations for constant acceleration.

We also now have new subscripts for velocity, depending on if it is vertical, horizontal or resultant.

The first part of the motion is between the initial point and maximum height.
Here the velocity along the vertical just decreases, but is still positive. Same with the angle of the resultant velocity. Of course the velocity along the horizontal is still the same.

The second part is at the top of its trajectory. Here vertical velocity is zero, the angle of the motion is zero, and the resultant velocity is equal to the horizontal velocity.

The third part was the between the top of the trajectory and returning to the original height. The vertical velocity is now decreasing and negative, and so with the angle of the resultant velocity.

I also emphasized that just like in the third scenario of freefall, the time it took for the object to go from a certain height to the top is the same as from the top back to the same height, and the horizontal displacement for each is also the same.

The last part is when the object is below the original height already, which is dependent on the kind of terrain that is used.

Here I had to show them the four types of trajectories we can have: for a flat plain, ending higher than the original height, ending lower than the original height or hitting a vertical surface.

I also gave them a sample table they were to fill out and plot to get a better idea of the motion.

Session 831 hits a wall at this point. Class dismissed.