Predicting the Landing Zone of a Projectile

Posted by: Scott on: October 27, 2009

• In: Demonstrations | Lab & Classroom Equipment | Lab Experiments
• 4 Comments

Let me start by saying that the kids really liked this lab.  It made them smile when they succeeded.

I kind of made this one up, kind of adapted it from the electronic timer manual.  The idea is that we use a ramp to accelerate a steel marble, have it pass through timer gates, measure the distance between the gates and calculate the velocity.  Do that a couple of times for accuracy.

Now measure the height of the table using a meter stick.  Use a fishing weight on a string to find the point directly under the edge of the table.  We now have the horizontal velocity, the height of the table, we can calculate how long it will take to fall.  Next we do the math and place a penny where the steel marble should land.

In the beginning, it would works sometimes, but not always.  I determined that our heavy epoxy table tops caused the steel ball to bounce, losing some of its horizontal velocity.  The bounce was easily dampened by placing two or three sheets of paper under the end of the ramp.  We also had some issues with hitting the side of the photogate.  Lining up the gates with the ramp was a minor issue, but an important one.  After the speed was determine, we moved the photogate away used the already calculated speed.

Here is the Lab as I wrote it up, it needs some updates like the paper under the ramp.  I realized later that I should have had the kids measure the starting height of the ramp.  Then we could go back to it later when we do energy and analyze the results.

Horizontal Projectile

Next year I think I will have them hit the penny first time, then a dime, then a small washer, so each time it must be more accurate.

As always, comments and ideas are welcome.

Tags: projectile motion