a,
$a= \frac{F}{m}= \frac{1000}{500}= 2 (m/s^2)$
$v_o= 0$
$\Rightarrow v= \sqrt{2as}= \sqrt{2.2.250}= 10\sqrt{10} (m/s)$
b,
$A= Fs= 1000.250= 250 000 (J)$
c,
$v= at \Leftrightarrow t= \frac{v}{a}= \frac{10\sqrt{10}}{2}= 5\sqrt{10} (s)$
$\Rightarrow P= \frac{A}{t}= 15811,4 (W)$