Answer:
0.275 m/s in the opposite direction
Explanation:
m = Mass of student = 50 kg
M = Mass of plank = 150 kg
[tex]v_r[/tex] = Velocity of the student with respect to the plank = 1.1i m/s
As the linear momentum is conserved in the system
[tex]m(v_r+v)+Mv=0\\\Rightarrow v(m+M)=-mv_r\\\Rightarrow v=-\frac{mv_r}{m+M}\\\Rightarrow v=-\frac{50\times 1.1i}{50+150}\\\Rightarrow v=-0.275i\ m/s[/tex]
The plank will move at 0.275 m/s in the opposite direction