Given:

$m=750 kg$

$u=0 m/s$

$v=3 m/s$

$S=4m$

$a=constant$

$v^2=u^2+2aS$

${\left(3\right)}^2=0+2\times{}a\times{}\left(4\right)$

$\therefore{}a=1.125\ m/s^2\ \uparrow{}$

Applying D’Alemberts Principle -

$\displaystyle\sum F_y=0$

$T-ma-mg=0$

$\therefore{}T=m(a+g)$

$=750\times{}(1.125+9.81)$

$T=8201.25\ N$