Skateboarder

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.’

Conditions A horizontal surface A skateboard A skateboarder

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

Explanation Ábra

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

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

Parameters – the surface μrolling must be the biggest μstatic

Parts of a skateboard

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

Trucks, wheels, bearings

Parameters – the skateboard Deck: smaller the better Trucks: loosely adjusted for better turning Wheels: soft, 60-75 mm Bearings: small friction

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

The right positions