Task 5

Materials and tools for a working group:

2 pendulums with different sized bobs with the same weight

The aim of the task is to find out whether the pendulum oscillation rate depends on how large pendulum bob we use. Pupils consider the following predictions:

• I think both pendulums will swing the same rate.
• I think, the swing of pendulum will be faster if the pendulum bob is bigger.
• I think, the swing of pendulum will be faster if the pendulum bob is smaller.

Inter alia, by carrying out both research tasks, the teacher creates a better idea of the difference between the volume and the weight of the object.

As in the previous task, it is appropriate to consider how to make two pendulum bobs that are equally heavy but of different size. However, it is important to alert pupils that they must also have the same shape. If the teacher does not have enough time, he or she can suggest the pupils concrete procedure of how to create such pendulum bobs. It is advisable to use a variety of materials, such as a ping-pong ball, which the pupils place on isosceles and balance the same weight of plasticine. They then make a ball out of the weighed plasticine so that both pendulum bobs have the same shape. Or use a plasticine ball and, for comparison, a hollow plasticine ball made of the same amount of plasticine. However, it is important to ensure that the difference in size of the weights being examined is large enough to trust the pupils.

Pupils then measure the number of swings for a larger and smaller pendulum bobs, and write the results in numerical form and then create a diagram from the numerical values. On the basis of the diagram they conclude and answer the research question.