Q & A: Skateboards and Physics

Q:
The Semester test for science is coming up and i need some help. :If you are riding on a skate board and it stops suddenly, your body keeps moving forward. Is this because of gravtity, mass, acceleration or something else?
- Anonymous (age 13)
McCallum Middle school
A:
You keep moving because of a property of matter called Inertia.

This property was described in Sir Isaac Newton's first law of motion.

The first law of motion states: All non-moving objects will remain non-moving and all moving objects will remain moving at the same speed in the same direction until acted upon by an external force.

External Forces could be a push, a pull, gravity, friction, etc.

So you ride on your skateboard and the skateboard suddenly stops because something acts upon it with a force. However, you keep moving because nothing has acted on YOU with a net force, just on your skateboard.

It's the same reason that seatbelts are on cars. If the car stops, you'll keep moving until acted upon by a force. That could be the force of the dashboard or windshield, or the force of the seatbelt, if you're being a good passenger.

Jason

(published on 10/22/2007)