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Question
Let F, FN and f denote the magnitudes of the contact force, normal force and the friction exerted by one surface on the other kept in contact. If none of these is zero.
(a) F > FN
(b) F > f
(c) FN > f
(d) FN − f < F < FN + f.
Solution
(a) F > FN
(b) F > f
(d) FN − f < F < FN + f
The system is in equilibrium condition when F = f.
Hence, the net horizontal force is zero.
f = μFN
F > FN
f = FN and 0 ≤ μ ≤ 1
Therefore, we can say that F > f. So the net horizontal force is nonzero.
F > f, and so the net horizontal force is zero.
FN > f ⇒ FN > μFN ⇒ μ < 1
Here, the given relation between F and f i.e
F > f and f = μFN will not be satisfied So it cannot be said that the net horizontal force is zero or nonzero.
FN − f < F < FN + f
∵ f = μFN
`f/mu-f<F<f/mu+f`
`f((1-mu)/mu)<F<f((1+mu)/mu)`
For the above relation, we can say that F ≠ f and so the net horizontal force is nonzero.
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