An astronaut in an orbiting spacecraft attaches a mass m to a string and whirls it around in uniform circular motion. the radius of the circle is r, the speed of the mass is v, and the tension in the string is f. if the mass, radius, and speed were all to double the tension required to maintain uniform circular motion would be
a) f/2
b) f
c) 2f
d) 4f
e) 8f