m1 = 10 kg
m2 = 20 kg
u1 = 10 ms-1
u2 = 5 ms-1
v1 = 12 ms-1
v2 = 4 ms-1
Time of collision, t = 2 s
∴ Force acting on 20 kg object
F1 = m2 \((\frac{v_2 -u_2}{t})\)
= 20 \((\frac{4 - 5}{2})\)
F1 = -10 N
Force acting on 10 kg object
F2 = m1\((\frac{v_1 -u_1}{t})\)
= 10 \((\frac{12-10}{2})\)
F2 = 10 N