Answer:
81.81 kg
Explanation:
[tex]m_1[/tex] = Mass of person = 78.4 kg
[tex]m_2[/tex] = Mass of canister
[tex]u_1[/tex] = Initial velocity of person = 0
[tex]u_2[/tex] = Initial velocity of canister = 3.5 m/s
[tex]v_1[/tex] = Final velocity of person = 2.4 m/s
[tex]v_2[/tex] = Final velocity of canister = 1.2 m/s
The momentum balance in the system is given by
[tex]m_1u_1+m_2u_2=m_1v_1+m_2v_2\\\Rightarrow 78.4\times 0+m_2\times 3.5=78.4\times 2.4+m_2\times 1.2\\\Rightarrow m_2=\dfrac{78.4\times 2.4}{3.5-1.2}\\\Rightarrow m_2=81.81\ \text{kg}[/tex]
Mass of the canister is 81.81 kg.