Question

7. Why rolling friction is less than the sliding friction?
A Direction of frictional force changes
B. Moving object becomes lighter
C. Because it is easier for a body to roll over another in comparison to slide
D. All of above.
8. Name the system which converts sliding friction to rolling friction?
A. Ball bearing
B. Airplane
C. Bus
D. None
9. Friction produces
A. Cooling
B. Ice
C. Steam
D. heat​

Answer 1

Answer:

7 (b)

8 (a)

9 ( d)

are the answers