Energy & Forces - Forces & their effects - Friction & Air Resistance - G16 - EF-C3.3 - Teacher's Guide

Energy & Forces - Forces & their effects - Friction & Air Resistance - G16

Teacher's Guide

EF-C3.3

2. Rather than talk about air resistance it is better to feel so if you have the right sort of weather...... Choose a blustery day and assemble a couple of inflated balloons, some thin strips of fabric of assorted thicknesses (three is plenty) and ask the children to put their coats on. Remind the children of basic rules for outdoor work and proceed outside. Gather the children around and ask them which way the wind is coming from. You can show them how to lick around a finger and hold it in the air to see which side dries but keep cleanliness in mind if you do this! Now ask the children to do up their coats tightly. Divide them into four teams and let them run across the playground and back as in a relay i.e. only one child from each team running at any one time. (Stress that this in not a race!) Ask the children how it felt a) running into the wind and b) running with the wind. Now repeat this with the children holding their coats open wide to trap air. How did this compare with the first time? Hold up the strips of fabric and talk about how they are affected by the wind. Does the light fabric go up higher than the heavy fabric and why? Now let a balloon go in the wind - a firm command of the children will be needed to make sure that they do not chase the balloon but stand on a line and watch it. Now find a sheltered spot in the playground - next to a wall or building and let the second balloon go. What happens now? Watch the balloon for a while because eddy currents of air running off the building may cause it to spiral and dance and move against the direction of the wind. Return indoors to talk about the wind.
4. Before making the parachutes, do a simple demonstration for the children. Take two pieces of A4 paper and scrunch one up into a ball. Drop both pieces simultaneously from the same height. The children should notice that the flat sheet of paper drops much more slowly than the balled up piece.
	They should be able to work out that molecules of air under the paper support it until they escape to the sides. The balled up piece has a much smaller surface area and so many fewer air molecules trying to support it and an easier route out to the side to escape.
Simple parachutes can be made using paper squares and stapling string or thread to each corner then tying the four threads onto a plastic cube or similar weight. This can be repeated with tissue paper, fabric, plastic sheet cut from a carrier bag etc. Remember to drop all the parachutes from the same height to get a fair comparison.
5. Factors to investigate include different heights for the drop, different weights as a ‘load’, different parachute sizes and different fabrics. Some commercial parachutes now have vents in the canopy for various reasons. The children could investigate what happens when various sized holes are punched in the canopy. It can be difficult to compare parachutes since children may not drop them simultaneously. Can the children think of a way to let the parachutes go at the same time? Perhaps lay them all on a table and sweep them off together using a metre rule....