Understanding some Properties of Projectiles

Forget the math for a few minutes - focus on some of the important concepts and interesting properties of projectiles, at least under ideal conditions (i.e. no air friction!). This gets into the importance of independent horizontal and vertical motions that are really the key to understanding projectile motion, and multi-dimensional motion in general. To understand why parabolic paths form, check out this video. To check out some basic math for projectile problems, check out this video.

Check it out, and hopefully this will make some sense to help you understand what the math is telling us when we do problems.

Projectile trajectories - With and Without Air Friction

All of us are familiar with the arch-shaped path, or trajectory, a ball follows when we throw it. When symmetric, this is a parabola, and is the common shape we use in physics classes for projectiles. But WHY is it an arch of any kind, let alone a parabola? And why are we lying to you about projectiles???

We ignore air friction when we do projectile problems, but in life this makes it more complicated, and also no longer a perfect parabola. Check out this video to get a sense of why parabolas form when there is no air friction, and what the trajectory looks like in a more realistic environment, with air friction.

How to do Relative Motion problems: Getting across a moving river

Relative motion has to do with multiple objects moving with respect to one another, and trying to think about how it all looks depending on what point of view different observers have when watching the objects.

A classic example of this is trying to get a boat across a flowing river, without being pushed off-course or downstream. How is this done? This is the same problem as trying to fly a plane when the wind hits it from the side, or a bird trying to fly on a windy day. What do you have to do to the boat, airplane or bird in order to not be pushed off-source?!

Check out this video to see how to use basic vector rules with the velocity vectors involved in the problem!

How to do Projectile Motion problems

Projectiles are objects that fly through the air or space, under the influence of gravity (and ignoring air friction for now), but not using any of its own energy to do so. It has been 'projected' by something else to start moving, like kicking or throwing a ball, shooting an arrow, a satellite, or even when you run and jump - you're a projectile once in the air!

Projectiles follow an arch, which is technically a parabola when there is no air resistance.

The key to understanding this motion is to realize there are two motions simultaneously: constant horizontal velocity, and constant vertical acceleration due to gravity. And when two things are perpendicular to each other, they are also independent of each other. Sideways motion could care less about what happens vertically, and vice versa!

Check out this video, which goes through two related projectile problems, and how to set them up.

Chem/Phys Reunion in September!!

We will have a Chem/Phys reunion on September 23, at ETHS. We are trying to get as many alums from as many decades as possible, and current students will be a part of this as tours of the classrooms and schools will be coming through. It can be a wonderful chance to meet people who were in your same seats years ago, and also start networking prior to going to college...you never know when there might be a summer internship or connection at a school you are looking at, etc. Save the date! And if a parent or sibling is an alum, pass this along! Check out https://eths.revtrak.net/Chem-Phys-Reunion#/list.

Studies Suggest We Should Expect More Lightning With Warmer Climates

For the past five or so years, one thing we've discussed in 4 Chem/Phys E&M is lightning. It is a naturally curious phenomenon for human beings, and simply really cool from the science perspective! But one aspect of this that most never think about is how lightning is related to climate change and a warming atmosphere. In the video we watch on lightning, it was surmised that the sheer number of lightning strikes should increase with warming - makes sense at first thought since moisture drives cloud and lightning production, and a warmer atmosphere should mean more moisture in the atmosphere. A relatively new study shows evidence for this prediction. If anyone is interested in this sort of thing, there could be some research possibilities! See me.

Malawi Fundraiser - GoFundMe for wells for crop irrigation

Thank you to the students who put together this GoFundMe campaign for our Malawi brothers and sisters! We have helped them get land, seed and fertilizer so schools can grow their own crops, but now, for long-term self subsistence, they need funds to drill wells and irrigate those crops when the next drought happens.

Check out https://www.gofundme.com/ethsformalawi. Even small donations matter A LOT, since $1 is some 730 kwacha!

A Shameless Plug for UIUC Engineering

Just because I went there...in reality, some say the College of Engineering is tops in the world. It certainly is among the most elite, with 16 top-5 programs!

Northwestern's work on Climate Change - A lot going on!!

If you have any interest in climate change and want to get a sense of the research efforts going into this important topic, or if you are interested in checking out research labs involved in these studies, you really need to read this extensive site outlining Northwestern's involvement in climate science! Let Doc V know if you want to learn more about any piece of this work.

Fractal planting patterns yield optimal crop yields

Some students have been intrigued by fractals. And the more we look around in Nature in all sorts of systems, we find fractal patterns develop. It appears that this is also true for crop yields and production. An interesting article about some patterns that have developed, without planning, indicate that optimal yields are nearly reached when fractal patterns are used. This could lead to some interesting research options!