Bombing the Enemy

F Block conducted a lab investigation on horizontally-launched projectiles. The mission was simple - use photogates to determine the velocity of a ball-bearing, take the height of the launch platform and determine where to place the target for the bearing to hit. The thing was, the bearing was only allowed to hit the ground once - when groups were ready to make their bombing run for me (and the rest of the class to see). This lab required careful measurements of horizontal velocity and height and careful calculation of the bearing's horizontal displacement. Groups did an excellent job - the targets were either nailed on the first go or with a little lateral adjustment of the target. The range calculations were fine, but the launch ramp and target were a little off right-left. Tomorrow, E Block sees if they can make as good a showing...

B and C Blocks reviewed the idea of projectiles launched horizontally and had class time to work practice problems for this type of motion. Remember that time is y-dependent and the most commonly used formula to find time for these problems is Δy = v_ot + 1/2at². Since the initial velocity in the y-direction is 0 m/s, the formula simplifies to: Δy = 1/2at². Once you have time, solving for horizontal aspects of the motion is simple. You've got one formula to use: v_x = Δx/t. You're generally asked for either horizontal displacement (and they give you v_x) or for launch velocity (and they give you Δx). Just use the time you found for the y-component of the motion and you're good as gold. We'll look over these tomorrow and then start to discuss projectiles launched at an angle. They take a bit more work, but it builds on what we've already done, so it won't be exhausting.

E Block had their full horizontally-launched projectiles chat today and also has a set of problems to work. We'll be going over those on Monday, since tomorrow is your lab block. I'd get them out of the way tonight for two reasons:

1. They will help you with you lab calculations tomorrow.


2. You'll have the lab write-up to do over the weekend, so don't give yourself double homework.

For everyone, the test is looking like it will be next Friday. That's a little later than I had planned but we're losing a couple of periods next week for various things, so c'est la vie...