Web videos that involve physics are fun to watch. They can be even more engaging with the addition of a few well-crafted questions.
This activity engages students with a dramatic video that captures the initial moments of a volcanic eruption. An adiabatic expansion cloud appears and disappears, a shock wave shocks observers capturing the video, and huge boulders trace graceful arc through the air, taking many seconds to eventually crash back into the ocean.
Mount Tavurvur Volcano Eruption Papua New Guinea 2014 (YouTube v=oMxIlXW56cQ)
Careful analysis of the video and knowledge of physics, and the use of PhET's Flash-based "Projectile Motion" sim allows students to determine the distance to the volcano and the launch speed of those boulders. How safe were the people filming the eruption? [At this time, PhET's HTML5 Projectile Motion sim is too limited to use with this activity.]
Add this to your mix of classroom demonstrations and lab activities to thoroughly teach the topic at hand. I developed this activity for use with my own students.
Summer 2020 UPDATE: In addition to the printable PDFs of the student blank and answer key, a Google Docs version of the student document now included for easier distance learning use.