Question

5.
Calculate the minimum force applied for which the
mass m stays at rest w.r.t the body of mass M.
р
m
M
smooth
(1) mg
р
(2) Zero
(3) m cannot be at relative rest
(4) (M+m)g/u
​

Answer 1

Answer: THE ANS SHOULD BE mg/µ

Explanation: The force applied by the gravity should be balanced by some other force so that the object of mass m stays in rest position ( in vertical direction)

Let the force F be acting on the block in upward direction which is the force of friction offered by the surface of both the masses having µ as  coefficient of friction

friction = µN = 0 .................... (1)

Normal force would  be 0 as there is no motion in the horizontal direction ( acceleration 0 ) there will be no friction

So for the object to stay at rest there should be some normal force which will be provided by external agent

Let us suppose the acceleration a is applied then the force be (M+m)a which will be equal to normal force

thus normal force will be N = (M+m)a

but the options contain ans in terms of g

Thus we will apply eq. 1

µN = mg

N = mg/µ

Hence the correct option will be option 1

Please mark the brainliest