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Predicting projectile trajectories
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| Subject Area |
mechanics, projectile motion |
| Age or Grade |
10th grade, 2nd year physics class |
| Estimated
Length |
60-120 min |
| Prerequisite
knowledge/skills |
kinematics of projectile motion, maybe solve quadratic equations |
| Description
of New Content |
calculate the distance of an actual projectile and test prediction |
| Goals |
apply knowledge about projectile motion, see physics laws actually work |
| Materials
Needed |
"canon ball" launcher with variable shooting angles and velocities. We had a spring powered marble launcher from Cambridge? available. The initial projectile speed was measured before the lesson |
|
Procedure
|
The
students were grouped in pairs and each pair was given an initial
velocity and launch angle. The were supposed to calculate the maximum
distance of a projectile trajectory starting with these values. They
could then test the predictions with the marble launcher by positioning
a sand filled box in the appropriate distance. The grade was supposed
to be determined by the accuracy of their prediction. Although the effects of air resistance were negligible over the short distances used, one has to make sure that especially the launch velocitiy can be reliably reproduced. Our setup showed slight variations in the launching speed leading sometimes to large discrepancies between students predictions and actual experiment outcome. However many students predictions were right on the landing point. The negative case can be used to discuss the limits of the experimental setup and error analysis. |
| Extensions |
Mathematically a little bit more complex is the problem when launching and landing height are not equal. (have to solve quadratic equation) This can be assigned to students who fnish the first task quickly |
| References |