Falling for science

Try these two activities to explore the effects of gravity on falling objects.

• 17 July 2006 | Updated 14 October 2011

• Activity 1: Balloon in a box
• Activity 2: Drop cup

In the following two activities you'll see how gravity affects falling objects. You may need an adult to help you put them together. Have fun and be careful!

Activity 1: Balloon in a Box

Warning: This activity includes the use of nails, a hammer, and a needle. Be careful with sharp objects. You may want an adult to assist you.

What you need

What will happen when you drop it?

To do this activity you will need:

• four pieces of plywood
• a balloon
• a lead sinker
• a needle
• rubber bands
• tape
• nails
• a hammer.

What to do

1. Put together a rectangular wooden frame.
2. Using elastic bands, suspend a lead sinker from the top of the inside of the frame so that the rubber bands are stretched. Attach an upward facing needle to the sinker.
3. Inflate a balloon and stick it to the top of the frame so the needle is suspended below the balloon.
4. Try dropping the frame from a couple of metres high with someone there to catch it so your construction isn't damaged when it hits the ground. What happens to the balloon?

What's happening

When an object falls the effects of gravity are cancelled out and an object experiences weightlessness. In this case, the frame and the objects inside become weightless. However, if the lead sinker becomes weightless, the elastic bands, which are stretched, will now pull the sinker up causing the needle to puncture the balloon.

Activity 2: Drop Cup

Many strange things happen with falling objects due to the effects of gravity being cancelled out. What's not happening in this experiment that you would expect to happen under normal circumstances?

It's best to do this experiment outside as it will make a mess.

What you need

To do this activity you will need:

• a styrofoam cup
• a pen or pencil
• water.

 What to do

What a difference a drop makes!

1. Fill a styrofoam cup with water and put a hole in the bottom side of the cup with a pencil. As you'd expect, water pours out (as in the cup on the left in the image).
2. Now drop the cup full of water. It's a good idea to have a bucket under the falling cup to prevent a mess when it hits the ground.

What's happening

The water becomes weightless while the cup is falling and, for the duration of the fall, it no longer pours out of the hole.

See if you can come up with your own falling demonstrations that might produce other interesting effects.

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