Answer:
53.54 Kg
Explanation:
We know that kinetic energy is given by [tex]0.5mv^{2}[\tex] where m is mass and v is the speed.
Let your speed be v and the speed of the friend will be 1.23v
Since kinetic energy is the same then
[tex]0.5\times84v^{2}=0.5m_u(1.23)^{2}\\\m_u=53.54 Kg[/tex]