Question

The normal reaction between the blocks $N_1,N_2$ are

• A. $50N,20N$
• B. $100N,50N$
• C. $50N,200N$
• D. $100N,20N$

Answer 1

The correct option is D $100N,20N$


Equation of motion for each Block:
all the three blocks will move together with common acceleration $\left(a\right)$
$N_2=5a⟶\left(1\right)$
$N_1-N_2=20a⟶\left(2\right)$
$200-N_1=25a⟶\left(3\right)$

Adding $\left(1\right),\left(2\right),\left(3\right)$
$(+)200=5a+20a+25a$
$200=50a$
$a=4m{s}^{-2}$

By substituting this acceleration value in the above equation of motion we can get $N_{1}and{N}_2$
$N_2=5\left(4\right)=20N$
$N_1-N_2=20a$
$N_1=20\left(4\right)+20$
$N_1=100N$