Ball bearings permit a wheel to turn freely on an axle without creating any heat because they form a mechanical system that involves
A)	no static friction.
B)	no sliding friction.
C)	no friction of either type.
D)	no electricity.
Answer:B
Ball bearings permit a wheel to turn freely on an axle without creating any heat because they form a mechanical system that involves
A)	no static friction. B)	no sliding friction. C)	no friction of either type. D)	no electricity.