This morning 22 year 9 students from Kenton visited Think Lab. They tried out a range of simple activities, all of which encouraged them to ‘Do Physics!’ Some of the explanations used physics ideas that they had met before, but some required them to think about topics which they won’t meet until A-level physics (or beyond). All were chosen to make the students go ‘Hmmm’ and think hard about what they had observed.
One of the activities was dropping different balls to see which reached the ground first. They had two tennis balls, one of which was filled with water. Lots of the students predicted that the heavier ball would fall faster.
It didn’t. Although it was hard to spot visually, when we listed for the balls hitting the ground, they bounced at the same time. This was quite surprising! Part of the reason for this is that ‘common sense’ tells us that heavier things fall faster. And if air resistance becomes a significant factor, then we do find that heavy things fall faster. The tennis balls take air resistance out of the experiment, and then the balls fall at the same rate.
A slightly larger demonstration of this phenomenon was done by Professor Brian Cox using a giant vacuum chamber.
Another very popular activity was looking at water beads, or hydrogel beads. These are a water absorbing polymer. When they are dropped into water, they disappear.
You can buy water beads online, or from florists shops.