Question

Three blocks m1,m2 and m3 of masses 8kg,3kg and 1 kg are placed in contact on a smooth surface.Forces F1=140N and F2=20N are acting on blocks m1 and m3 respectively.The reaction between blocks m2 and m3 is
A)2.5N
B)7.5N
C)22.5N
D)30N

Answer 1

Answer:

Explanation:1st find net force on system then find net acceleration of the system and then draw fbd of each block with proper explanation

Answer 2

Answer:

The reaction between blocks m2 and m3 is 30 N.

So option D is the correct answer.

Explanation:

We know that, the acceleration of the system will be

$a_{sys}= \frac{∑F}{total \: mass}$

$a = \frac{F_1 - F_2}{m_1 + m_2 + m_3} = 10 \: m {s}^{ - 2}$

and the whole system moves towards right.

Now for the reaction between $m_2 \: and \: m_3$,

By the newton's law equation, here

R is the reaction force on the block $m_3 \: by \: m_2$

$R-F_2=m_3a→R=20+1 \times 10 = 30$

The reaction between blocks m2 and m3 is 30 N.