Which two surfaces would have the lowest coefficient of friction?
a. ice on ice
b. rubber on dry concrete
c. glass on glass d. wood on wood

A. Ice on ice

Explanation:

Coefficient of friction explains or estimates the relationship between two objects in terms of the force of friction between them and the normal reaction between these two objects. Depending on the objects involved, coefficient of friction varies from surfaces to surfaces. Rougher surfaces tend to have greater coefficient of friction compared to smoother surfaces. Therefore in the options provided, ice on ice tends to have the smoothest surfaces contact  and thus will have the lowest coefficient of friction.

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blue light is scattered in different directions by the tiny molecules of air. blue is scattered more than other colours because it has a shorter distance to travel which results in smaller waves. this is why we see a blue sky most of the time.