The experimenting stage, since the scientist would need to record his or her data on a chart
Heat makes things expand, so in hot water the ballon will get bigger
Given :
An object 50 cm high is placed 1 m in front of a converging lens whose focal length is 1.5 m.
To Find :
the image height (in cm).
Solution :
By lens formula :

Here, u = - 100 cm
f = 150 cm

Now, magnification is given by :

Therefore, the image height is 3 m or 300 cm.
When wool is rubbed with a balloon, the wool is left with a positive charge as electrons have travelled from the wool to the balloon which means the balloon now has a negative charge.
Now that the balloon has a negative charge, you need to know:
The tissue paper originally contains electrons and protons
The fact that the balloon has a negative charge, it will ATTRACT protons because protons are POSITIVE and electrons are NEGATIVE.
So once they are attracted, they will move closer to one another.