A skateboarder is attempting to make a circular arc of radius r = 19m in a parking lot. The total mass of the skateboard and skateboarder is m = 81kg. The coefficient of static friction between the surface of the parking lot and the wheels of the skateboard is _s = 0.51.

Questions:

1a: What is the maximum speed, in meters per second, he can travel through the arc without slipping?

1b: He speeds up very slightly and begins to slide. The coefficient of kinetic friction is _k = 0.19. What is the new magnitude, in meters per second squared, of his radial acceleration?