• # question_answer A man (mass = 50 kg) and his son (mass = 20 kg) are standing on a frictionless surface facing each other. The man pushes his son so that he starts moving at a speed of $0.70\,m{{s}^{-1}}$ with respect to the man. The speed of the man with respect to the surface is : [JEE Main Held on 12-4-2019 Morning] A) $0.20\,m{{s}^{-1}}$ B) $0.14\,m{{s}^{-1}}$ C) $0.47\,m{{s}^{-1}}$ D) $0.28\,m{{s}^{-1}}$

 [a] $\Rightarrow 0=50{{V}_{1}}-20{{V}_{2}}$and${{V}_{1}}+{{V}_{2}}=0.7$$\Rightarrow {{V}_{1}}=0.2$