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# Combining Forces

## The net force acting on an object is the combination of all of the individual forces acting on it.

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Ollie Up

### Ollie Up

Credit: Valya Egorshin
Source: http://www.flickr.com/photos/valya_v/5837575108/
License: CC BY-NC 3.0

If you know anything about skateboarding, you probably know that this skater is doing a trick called an Ollie. Maybe you know how to do one yourself. If not, you may be asking, “How does he get the skateboard to ‘stick’ to his feet?” The trick can be explained by simple physics.

News You Can Use

• The Ollie was invented in the 1970s. Since then, it has become a basic skateboarding trick.
• A skater needs to master the Ollie in order to do many other tricks on a skateboard. The Ollie is also useful because it lets the skater jump over obstacles and up onto curbs.
• How does a skater get the skateboard to jump up into the air? You can see how to do an Ollie in this video: http://www.exploratorium.edu/skateboarding/ollie_video.html

Can You Apply It?

With the links below, learn more about the physics of the Ollie. Then answer the following questions.

1. Before a skater performs an Ollie, what three forces are acting on the skateboard? What is the net force acting on the board?
2. How does the skater get the board to tilt backward so the tail strikes the ground? What happens to the skateboard next?
3. How does the skater drag the board higher into the air?
4. How does the skater cause the board to level out in the air before falling back down to the ground? How does the skater make it appear that the board is attached to his feet?

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