Question

A block of mass 4 kg lies over a horizontal surface. Another block of mass 2 kg is placed over the first block. The normal reaction between the lower block and ground surface is (g = 10 ms-²)​

Answer 1

Answer:

60 N

Explanation:

We only need normal force on ground not between the blocks , so take both blocks as system lying on ground . So total mass of system = 2 + 4 = 6 kg . Just think it's a giant block of 6 kg not two saparate blocks .

Now on 6 kg system there are only two forces

6 × 10 = 60 Newton gravity downwards and Normal force N from ground . Since block is not moving at all so these two forces are in equilibrium i.e. N = 60 Newton and opposite direction of gravity .

Answer 2

A block of mass 4 kg lies over a horizontal surface. Another block of mass 2 kg is placed over the first block. So, consider the two blocks to be a single system of mass.

Now, the net mass placed on the floor = 4 + 2 = 6 kg.

Hence, the net weight (W) = 6g = 6 × 10 = 60N.

Now, according to the FREE BODY DIAGRAM, we can say:

$\therefore \: N = W$

$\implies\: N = 60 \: Newton$

So, net reaction force is 60N.