A car travels around 200 m radius flat curve at 40 m/s at constant speed. What is the minimum static coefficient of friction which allows it to travel at this speed without sliding?.

On solidification from a melt, the polymer polyethylene forms a semi-crystalline spherulite structure. (i) sketch an individual spherulite and label the amorphous and crystalline regions. (ii) draw a schematic to show the changes in specific volume with temperature during cooling from the melt, comparing it to the theoretical extremes of fully crystalline and fully amorphous (indicate tm and tg)