A 10 g steel marble is spun so that it rolls at 150 rpm around the inside of a vertically oriented
steel tube (coeﬃcient of static friction is 0.8, coeﬃcient of kinetic friction is 0.6). The tube,
shown in Figure P8.39, is 12 cm in diameter. Assume that the rolling resistance is small enough
for the marble to maintain 150 rpm for several seconds. During this time, will the marble spin in
a horizontal circle, at constant height, or will it spiral down the inside of the tube? If the marble
spins in a horizontal circle what is the magnitude of the force of friction?

Question

A 10 g steel marble is spun so that it rolls at 150 rpm around the inside of a vertically oriented 
 steel tube (coeﬃcient of static friction is 0.8, coeﬃcient of kinetic friction is 0.6). The tube, 
 shown in Figure P8.39, is 12 cm in diameter. Assume that the rolling resistance is small enough 
 for the marble to maintain 150 rpm for several seconds. During this time, will the marble spin in 
 a horizontal circle, at constant height, or will it spiral down the inside of the tube? If the marble 
 spins in a horizontal circle what is the magnitude of the force of friction?

anonymous · Answer

If the marble spirals 
 down how much larger would the coeﬃcient of friction need to be in order for the marble to 
 spin in a horizontal circle?

anonymous · Answer

isn't figure there..,

anonymous · Answer

Sorry there isnt supposed to be a figure, it just says that in the question.