When students use small cut-out models to check for changes in the length of a shadow, they often find little change from hour to hour. So, why not ‘super size’ the model to make the changes more obvious? Including a thermometer on the cardboard cut-out allows for the identification of a temperature change as well as relating temperature change to the length of the shadow and the position of the sun.
The following experiment will give you insight into the role air pressure plays on weather and help explain how airplane wings get ‘lift’. Have you ever put your hand outside the window of a moving vehicle? As you are doing this, hold the palm of your hand flat or parallel to the ground and slowly rotate your hand until it is perpendicular to the ground? Did you notice that with a slight rotation of your hand, as the wind hits your palm, your hand was forced up by the wind? This is what will happen to the balloon as the air from the hair dryer passes over the balloon’s surface. The balloon is hit by the flowing air, which flows around the outside surface of the balloon, pushing the balloon into the centre of the air column created by the hair dryer. The balloon with receive lift until gravity exceeds the force being applied by the air from the hair dryer. As the balloon sits in this stream of air created by the balloon, a low-pressure area is created on the opposite side of the source of the air flow, leaving an ‘empty’ space behind the balloon. It is there because the wind is being blocked by the surface of the balloon. The air rushing over the balloon turns to fill up the low-pressure space, and then tries to keep on going—out the side of the main column. As the jet of air rushes ‘out’ over the surface of the balloon, it is pulled back onto the opposite side of the balloon, keeping the balloon inside the air column generated by the hair dryer.
Thanks to Flinn Scientific Canada Inc for making this resource available
Paraplegics could be given greater mobility, homes full of bugs, olive oil and bulletproof fabrics, taser shock disrupts brain function, artists interpreting science, gravitational waves spotted, floating ice shelves critically important – just a few of the themes in today’s eclectic collection of SciNews. Share these stories with your students and get them excited about science.