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Subject :NSO    Class : Class 8

In which of the following cases the friction is helpful (H) and troublesome (T)?
(A) Lighting a matchstick
(B) Applying the brakes on a cycle
(C) Use a towel to open tightly closed lid of a bottle
(D) Pulling drawer out of a desk

(A) (B) (C) (D)
A T T H H
B H H T T
C T T T H
D H H H T


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