3 CHANGING THE MOVEMENT OF AN OBJECT REQUIRES A NET FORCE TO BE ACTING ON IT

Task 12

WORKSHEET

Materials and tools for a working group:

objects of various shapes – balls, cubes, hollow hemisphere, egg – shaped (made of same material), plate, wheeled board (or slingshot)

The twelfth task focuses on exploring air resistance. It is not named directly, pupils examine it in order to determine whether the object of another shape goes further. The research can also be carried out using a sling, where the pupils compare the impact of a ball-shaped object, a cube, a hollow hemisphere and an egg, after firing in the same direction, with the same force.

As it is not a measurement, but a comparison, it is important to advice pupils that if I want to know which object is going to move the board fastest, we have to compare two and two and then winning two of them. The task is to create specially designed tables for recording the results that lead the pupils in the comparison process to answer the research question. Pupils find out which shape of the object (ball, cube, hollow hemisphere and egg) causes the moving platform to slow down. It is important to use objects of approximately the same size made of the same material (polystyrene is proposed, which can optionally be frictionally rubbed to the desired shape and is relatively easy to mount on a sloping platform) to realize that if we want to see if the shape of the object can slow down the movement of the object, we only need to change the shape of the object, not its size and weight.

Pupils should find out that shape of the object affect its movement, for example, a hollow hemisphere facing the forward opening significantly slows the movement of the object across the board. On the contrary, the ball and the egg (especially when it is turned forward with a blunt end) hinder the moving object less. These findings should be consistent with the results of air resistance measurements of various body shapes (see figure).