Overview

In this activity, students will find the muzzle velocity of a foam dart gun and predict its maximum range.

The instructor begins by showing the students the dart gun (which fires harmless foam darts), firing a few darts in demonstration. In small groups, pairs, or individually, students are asked to find the relationship between the muzzle velocity and the time taken by the projectile to return to its original position if fired directly upward.

The instructor gives a mini-lecture on uncertainties and measurements, then asks students to measure a time interval ("3, 2, 1, start... 3, 2, 1, stop"), creating a list of values measured by ...

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In this activity, students will find the muzzle velocity of a foam dart gun and predict its maximum range.

The instructor begins by showing the students the dart gun (which fires harmless foam darts), firing a few darts in demonstration. In small groups, pairs, or individually, students are asked to find the relationship between the muzzle velocity and the time taken by the projectile to return to its original position if fired directly upward.

The instructor gives a mini-lecture on uncertainties and measurements, then asks students to measure a time interval ("3, 2, 1, start... 3, 2, 1, stop"), creating a list of values measured by the students. The instructor can either select several (4-6) students with smartphones/stopwatches to take the measurements or have everyone in the class take the measurements and select some at random. The instructor creates a list of the values, then guides the class through the process of eliminating outliers and finding the average value.

Next, the instructor counts down and fires the dart gun directly into the air, with students measuring the time. The instructor again lists the measured times and guides students through the process of finding the average value.

Students are then asked to calculate the muzzle velocity of the dart gun. Once found, they use this value to calculate its maximum range.

As a class, the predicted range is measured and denoted either using chalk or by having a student stand at the maximum range. The instructor, holding the dart gun near the floor at a 45 degree angle, fires it. Students can then compare their predicted result with the actual result.

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Objectives

Students learn to identify outliers in measurements and to calculate mean values. They also apply their knowledge of projectile motion and the range equation.

Context and requirements

Level Grade 12-U0
Discipline Physics
Course Mechanics
Activity Content Projectile Motion
Technological Requirements Foam dart gun
Best Use Practice, Review

Author’s Notes

Benefits

This is a great, simple, real life example of using physics to make predictions and test those predictions. It also introduces students to the idea of measurement uncertainties. It can be done in a very large class, and is almost impossible to get wrong.

Challenges

Make sure you test it beforehand, low ceilings can be a problem for this activity.

Tips

You can either choose several volunteers to take the measurements, or if you’d like to involve more people have all the students take measurements and choose a few at random.

Activity Pedagogical Components

Problem Solving

In GROUPS or INDIVIDUALLY, students find an expression relating the muzzle velocity of the dart gun to the time taken for the projectile to return to its original height when fired directly upward. This is completed IN CLASS.

Data Collection

As a CLASS, time measurements are collected for an arbitrary measurement (the instructor counting down twice). The instructor leads students through the elimination of outliers and finding the mean value. This is repeated for the measurement of the dart gun being fired into the air. This is completed IN CLASS.

Problem Solving

In GROUPS or INDIVIDUALLY, students determine the muzzle velocity of the dart gun using the measurements. They then predict the maximum range of the dart gun. This is completed IN CLASS.

Consolidation

As a CLASS, the students’ predictions are put to the test. This is completed IN CLASS.

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