Stories from Physics for 11-14 14-16
Researchers have recently attempted to answer the questions of why the largest animals are not the fastest. They suggest that the relationship between speed and body mass follows a hump-shaped distribution. An animal’s maximum speed is limited by the time available for acceleration which is dependent on the amount of fast-twitch fibre an animal possesses and their ability to store energy. For example, small animals such as mice may possess the ability to accelerate rapidly but cannot sustain that acceleration for long, so their maximum speed is relatively low. Elephants, by contrast, cannot accelerate as quickly as mice but can maintain their acceleration for longer periods. Animals of medium size, such as cheetahs and marlins, therefore, are found to have the highest maximum speed. In applying their models to dinosaurs, the researchers predict that the maximum speed of a velociraptor would have been 55 km/hr, tyrannosaurus 27 km/hr and triceratops 24 km/hr.