Question

44. Block A of mass m rests on the plank B of mass 3m which is free to
slide on a frictionless horizontal surface. The coefficient of friction
between the block and plank is 0.2. If a horizontal force of magni
tude 2 mg is applied to the plank B, the acceleration of A relative
to
the plank and relative to the ground respectively,
are :
a)0,g/2 b)0,2g/3 c)3g/5,g/5 d)2g/5,g/5​

Answer 1

Answer:

Hey Buddy here's ur answer

2g/5 , g/5

Answer 2

Given :-

Mass of block A =${m}_{A}$= m

Mass of block B =${m}_{B}$= 3m

Coefficient of Friction = μ = 0.2

For mass A w.r.t mass B.

f = μ${m}_{A}$g

${m}_{A}{a}_{A}$ = μmg

${a}_{A}$ = 0.2 × 10

${a}_{A}$ = 2 ms-²

Multiplying and dividing by '5'.

${a}_{A} = \dfrac{10}{5} = \dfrac{g}{5}$

Again, For mass B w.r.t ground.

a' = Net Force/Total Mass

a' = 2mg/4m

a' = g/2

Since, a' > ${a}_{A}$

${a}_{B}$ = F - f/m

${a}_{B}$ = 2mg - 0.2mg/3m

${a}_{B}$ = 3/5 g

Again,

${a}_{AB}$ = g/5 - 3g/5

${a}_{AB}$ = -2g/5

Here, Negative sign indicates backward motion of body.