Question

A force of magnitude 7.50 N pushes three boxes with masses
m1 = 1.30 kg, m2 = 3.20 kg and m3 = 4.90 kg as shown in Figure 5–20. Find the magnitude of the contact force (a) between boxes 1 and 2, and (b) between boxes 2 and 3.

Answer 1

$$F=(m_1+m_2+m_3)a\\7.5=(1.3+3.2+4.9)a\\a=0.798\frac{m}{s^2}$$

1)

$$F_{12}=(1.30) (0.798) = 1.04\ N$$

2)

$$F_{23}=(3.20) (0.798)+1.04=3.59\ N$$