## Friday 8 December 2017

### Helicopter Test flights!

When objects fall through air, they accelerate due to the pull of gravity before reaching a constant rate of fall called terminal velocity. Terminal velocity is reached when the gravitational force pulling an object downwards is equal and opposite to the air resistance pushing it upwards and there is no more acceleration.

Parachutes increase a skydiver’s air resistance, or the upward push they receive from the air. This reduces their terminal velocity to a safe level. The same forces affect a paper helicopter—the larger the wings and the lighter the helicopter, the slower it will fall. Adding weight, such as, adding paper clips to the stem, or using heavier paper will make the helicopter fall faster because of the increased pull of gravity. Increasing its wing size will make it fall more slowly because of increased air resistance on the larger surface area.

As air moves past the falling paper helicopter, it creates a spinning effect. The air pushes up each wing separately, which causes the helicopter to spin.

In our investigation we looked at ‘What happens to the helicopter fall time when we change the wing size?’ Each team had to:
• change: the size of the wings using post it notes and the weight of the wings using paper clips
• observe: which helicopter hits the ground first
• keep the same: the shape of the wings, angle of the wings, stem length, release height

Students were able to observe that the helicopter with bigger wings fell more slowly and that the helicopter with smaller wings fell more quickly. When they added weight to the wings of one of their helicopters, it fell much quicker to the ground, due to the pull of gravity on the helicopter.

Here are some photos from our experiments.