Apparatus: A ruler, a computer, some string, cardboard a length of transparent tubing and some balloons.

1. The classic falling ball experiment with a balloon.

What is the relationship between fall time and height?

Simple treatment assumes constant velocity based on drag and buoyancy but this ignores the initial acceleration which is not constant. This can be modeled using an iterative model in Excel.

2. Balloon drop with different sized balloons.

What is the relationship between terminal velocity and diameter?

Measure terminal velocity with video analysis. Use stokes law to derive equation for terminal velocity but find it doesn't give a good fit.

3. Balloon pendulum (1)

What is the relationship between damping coefficient and diameter?

Damping coefficient is related to drag which is related to size of balloon. Use video to plot damped oscillations to find the damping coefficient.

4. Balloon pendulum (2)

What is the relationship between time period and length?

Simple theory as for the simple pendulum but not so simple due to damping, expect lower frequency than non damped. Also if string is quite thick it's mass will not be negligible and will change the centre of gravity of the system. Buoyancy may also affect the time period.

5. Charged balloons (1)

Hang two charged balloons from the same point, they will repel each other

What is the relationship between the length of string and the distance between two charged balloons?

Balance electric and gravitational forces to derive an equation. Charge will leak out of the balloons. Does it matter if balloons have different charge?

6. Charged balloons (2)

Same as above but allow air to escape and measure the distance between the balloons.

What is the relationship between the diameter of the balloons and the diameter?

Haven't thought this one trough but changing the size will change the mass and the buoyant force. The unexpected bonus is that reducing the size also reduces the charge. Would lead to some interesting discussion.

7. The balloon as a projectile (1)

Make a balloon launcher using a toilet roll. Launch with same velocity at different angles.

What is the relationship between angle and range?

Treat as a simple projectile to derive equation but find that air resistance plays a big part. Possible to model with Iterative model in Excel.

8. The balloon as a projectile (2)

As above but launch vertically varying the pull back

What is the relationship between how far the launching string is pulled back and height?

Use conservation of energy and Hooke's law to derive equation but find that air resistance can not be ignored.

9. The balloon as a projectile (3)

Launch at the same angle but vary the pull back and measure range?

What is the relationship between how far the launching string is pulled back and height?

Use conservation of energy and Hooke's law to derive equation but find that air resistance can not be ignored.

10. Balloon as a jet engine.

Attach a tube to the balloon and use it to blow of a freely hanging card.

What is the relation between the pressure in a balloon and the force exerted by the air expelled from it?

The pressure can be measured using a simple water manometer and the force by the angle that the card is lifted to when blown. Use Bernoulli and the balanced forces on the card to derive a relationship.