This is a satisfyingly simple activity with surprising results. Take a tennis ball and place it on top of a basketball… then release both at the same time.

Instant ball launcher!

You’ll find the top ball rockets off skyward while the lower ball hit the floor flat (without bouncing much, if at all). Now why is that? It’s easier to explain than you think…

Remember momentum? Momentum can be defined as inertia in motion. Something must be moving to have momentum. Momentum is how hard it is to get something to stop or to change directions. A moving train has a whole lot of momentum. A moving ping pong ball does not. You can easily stop a ping pong ball, even at high speeds. It is difficult, however, to stop a train even at low speeds.

Mathematically, momentum is mass times velocity, or Momentum=mv.

One of the basic laws of the universe is the conservation of momentum.  When objects smack into each other, the momentum that both objects have after the collision, is equal to the amount of momentum the objects had before the crash. Once the two balls hit the ground, all the larger ball’s momentum transferred to the smaller ball (plus the smaller ball had its own momentum, too!) and thus the smaller ball goes zooming to the sky.


  • two balls, one significantly larger than the other
Please login or register to read the rest of this content.

Have a question ?

Tell us what you're thinking...


11 Responses to “Rocket Ball Launcher”

  1. emilyannejon says:

    It kept my little brother entertained 4ever! 🙂

  2. Kathy Funk says:

    Google Chrome – I’ll try a different one.

  3. What type of web browser (and version) are you using?

  4. Kathy Funk says:

    Why can’t I download the worksheet on these experiments?

  5. I used 4 balls!:)

    Josiah age 11

  6. Laura Savel says:

    I saw it on TV it’s really cool I’m going to see if we have a tennis ball and a basketball (with the right amount of air).
    ~ Kristian

  7. Great question! What do YOU think?

  8. Emily Crawford says:

    I would like to know why this only seems to work with balls, and not with other objects. Is it just the shape? What else does this trick work with?

    Mary Crawford (age 12)

  9. Emily Crawford says:

    Awesome! I found that a baseball, when dropped from about four feet up, will only bounce two inches at most. But a baseball on top of a volleyball in this experiment… instant skyrocket!

    Mary Crawford (age 12)

  10. Theresa Getubig says:

    I’VE DID this a bunch of times its so fun and i did it with a bunch objects

  11. amanda young says:

    Keep your head back on this experiment. I was hit in the eye by the tennis ball when it came up. You might want to wear safety glasses when using the small bouncy ball!! ~Sam