My Favorite Web Applications - Part 7

Previous posts:

My favorite web applications - Part 1

My favorite web applications - Part 2

My favorite web applications - Part 3

My favorite web applications - Part 4

My favorite web applications - Part 5

My favorite web application - Part 6

This one is an obvious one. It is from PhET, and it is on projectile motion (the "Lab" option).

I have used this web app in many different situations and for many different purposes, including using it as a virtual lab when we went remote. However, even in my face-to-face classes, I continue to use this during our lessons on projectile motion.

One of the most difficult concepts for students to understand with projectile motion is that the maximum height and the time-of-flight of the projectile depends only on the vertical component of the motion. If the vertical component of the motion remains the same, then regardless of what the horizontal component is doing, the maximum height and time-of-flight will be the same as well.

What I typically have the student do with the app is the following:

• Set the canon to an angle of 30 degrees with respect to the horizontal and an initial speed of 20 m/s.
• Fire away!
• Measure the maximum height and the time of flight using the tools available in the app.
• Then change the angle to 90 degrees and an initial speed of 10 m/s.
• Fire away!
• Again, measure the maximum height and time of flight.
• Compare the two situations.

The students will find that for these two different situations, the maximum height and the time of flight are the same. I ask them to discuss this with their partner/s and figure out why these values come out this way. Then I ask them to find another angle and initial speed where the projectile gets to the same height and has the same time of flight.

Of course, the reason for this is that the vertical component of the initial velocity is the same for both situations. The is the only thing that the two motion has in common. Thus, since the maximum height and time of flight depends only on the vertical motion, the two different situations will naturally produce the same values for each of those two quantities. If they understand this, then they will be able to quickly find another angle and initial speed via simple calculation rather than by trial-and-error.

BTW, watch this space as I will be posting a link to an upcoming blog post of my interaction with ChatGPT on this same question that I ask my students.

Edit: This is my blog post on what happened when I asked this projectile motion question to ChatGPT.

Zz.