Juice Box Jetpack!

• Posted on 4 April 2020
• By Hema and Eric Bulmer
• Posted in action, motion, newton, reaction, third law

Observe Newton's 3rd Law of Motion (Action/Reaction) in cool new way! This is a great experiment to perform after a snack!

Juice Box Jetpack!

Objective

To observe Newton's 3rd Law of Motion (Action/Reaction) in cool new way! This is a great experiment to perform after a snack!

Materials

• Empty Juice Box
• String
• Water
• Something Pointy
• Something Sharp

Procedure

1. Drink your juice.
2. Fold the flap on the top of the box up. You may have to pry up the corner flaps also. Using something sharp, cut open the top of the juice box and open it right up like a milk carton.
3. Using something pointy, poke holes in the top flaps of the juice box (see diagram).
4. Using something pointy, poke a hole in the lower right corner of the front AND in the lower right corner of the back of the juice box. In the diagram, you can see the hole in the lower right corner.
5. Pass the string through both top-holes and knot the string so that the box is hanging from the string — the top of the box should still be open.
6. Bring water and your juice box-on-a-string and stand over a sink, outside, or over a container - somewhere you don't care about getting wet.
7. THE TRICKY PART: TEAMWORK REQUIRED! One person holds the water in one hand and the hanging juice box (hold by the string) over the large container on the floor. The other person locates the two little holes in the bottom right corners of your juice box and covers them with their fingers.
8. The person holding the water pours the water into the top of the juice box.
9. The person covering the holes lets go!

What happens?

Water should shoot out of the holes and cause the juice box to spin until the water runs out.

What's Going On?

When you let go of the holes in the juice box, the water rushes out—that is a force. As the water leaves the carton, it pushes back on the carton with a second, equal force, just as the fuel burning out of a rocket propels it forward.

Think and Talk About This

Look carefully at where the holes in the bottom of the box are located. Are they on the same side? Opposite sides? Would this experiment work differently if both holes were on the same side of the box?

© Hema and Eric Bulmer. All rights reserved.