In this lab you will shoot a chopstick across the room with a rubber band and measure how different variables affect the distance it flies. You will use concepts of kinetic and potential energy to understand how the chopstick is propelled.

**Download the labs!**

###### Student Version

###### Student Advanced Version

###### Teacher Version

**Recommended Prerequisites:**

- Students doing the advanced version of this lab should be comfortable with basic algebra, proportionality, square roots, and arithmetic.

**Key Concepts:**

- A
**projectile**is a flying object given an initial push. The distance a projectile travels depends on how fast it flies and how much time it takes to hit the ground. - Conservation of energy: When you stretch a rubber band, you store
**elastic potential energy**. The farther you stretch, the more elastic energy is stored. This can then be converted into**kinetic energy**(energy associated with motion) to make a projectile fly. The more kinetic energy it has, the faster it flies. - The kinetic energy of an object of mass
*m*, moving at velocity*v*is KE = 1/2 mv² - Physicists can come up with mathematical equations to describe real-world phenomena by using the concept of
**“proportional to”**or**“scales as.”**We say “x is proportional to y”, or write “𝑥 ∝ 𝑦”, if x is equal to y times some constant.

**Materials:**

###### For each group (2-4 students per group) you will need the following:

- 1 wooden chopstick
- Mark the tail end at 1 cm intervals (up to 5 cm).
- Test your projectile before running the lab. If the chopstick flies too far (i.e., if it hits a wall before hitting the ground), you can add a couple of metal nuts to the tip to reduce the distance the chopstick will fly.

- 1 pint-sized milk carton
- 1 pair of scissors or knife that you can use to make holes in the milk carton
- 1 meter stick or tape measure
- masking tape
- 1 balance, consisting of a wooden or cardboard bar with a hole at the center and two holes equidistant from the center, with a Ziploc bag attached to each edge hole (some wooden rulers already have holes punched for making such a balance)
- 1 rubber band (standard 5 mm size or similar)
- several grams of Play-Doh or modeling clay
- stack of textbooks or other props to increase the launch height
- a flat table or desk of reasonable height, with at least ~3 m free space in front of it
- ideally, 1 calculator per student; at a minimum, 1 per group