Question

(II) A 20.0-kg box rests on a table. (a) What is the weight of the box and the normal force acting on it? (b) A 10.0-kg box is placed on top of the 20.0-kg box, as shown in Fig. 4–43. Determine the normal force that the table exerts on the 20.0-kg box and the normal force that the 20.0-kg box exerts on the 10.0-kg box.

Answer 1

*Fig is Attached with answer*

Answer:

(a)   Weight = Normal Force = 196.2 N

(b)   Normal force table on 20 kg box = 294.3 N

       Normal force 20 kg box on 10 kg box = 98.1 N

Explanation:

(a)   Mass = m = 20 kg                           g = 9.81 m/s²

      Weight = w = mg

                      w = 20 × 9.81

                      w = 196.2 N

As the box rests on the table so, normal force (NF) must be equal to the weight of the box.

                    NF = w = 196.2 N

(b)

m₁ = 20 kg                      m₂ = 10 kg

total mass = M = 30 kg

Total Weight = W = Mg  

                             = 30 × 9.81

                             = 294.3 N

As both the boxes rest on the table so, normal force (NF) must be equal to the total weight of the boxes.

                          NF = W = 294.3 N

Weight of 10 kg box = 10 × 9.81 = 98.1 N

As the 10 kg box is placed on the top of 20 kg box, So 20 kg box must exert a normal force that is equal to the weight of 10 kg box.

              Normal Force = Weight of 10 kg box = 98.1 N