Question

10 Boxes each of mass 1 kg are placed one above the other as shown in figure then

Answer 1

Let assume both blocks are moving with different acceleration,

a1 = acceleration of block A

a2= acceleration block B,

From FBD of Block A,

F−f=ma1,     ......1

f=μN, N=mg, ⇒f=μmg= .5×10×10= 50,

Using value of f  in equation 1, 

⇒a1=0 , So our assumption is wrong. 

We take both block as system, let acceleration is a, 

F=2ma ⇒2×10×a=50 ⇒a=2.5ms−2

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Digit is different same as your question....