1. Skateboarder

2. The problem
‘A skateboarder on a horizontal surface can accelerate from rest just by moving the body, without touching external support. Investigate the parameters that affect the motion of a skateboard propelled by this method.’

3. Conditions
A horizontal surface
A skateboard
A skateboarder

4. Getting into move
A toy for children – the ‘moonwalker’

5. Explanation
Ábra

6. Determining factors
Way of driving: steering with 30 to 60 degrees; not too fast
Surface: e.g. tiles or parquet
Rolling friction: between floor&wheels and wheels&bearings
Driver: mass; motion

7. Starting a skateboard Raise it and turn →Gaining potential energy
Put it back onto the floor
Push
Repeat on the other side
→Gaining potential energy
→Converting into kinetic energy
→Getting into a circular motion
→ Accelerating

8. Parameters – the surface
μrolling
must be the biggest
μstatic

9. Parts of a skateboard

10. Forces acting on the wheels
We raise and move the nose rightwards
The wheels push the floor
The floor exerts a reaction force on the wheel
One component rotates the wheel
The other component causes a circular motion

11. Trucks, wheels, bearings

12. Parameters – the skateboard
Deck: smaller the better
Trucks: loosely adjusted for better turning
Wheels: soft, mm
Bearings: small friction

13. Parameters – the skateboarder
Small mass
Low centre of gravity
Leaning towards the centre of motion
The human factors are not negligible

14. The right positions