#### Answer

(a) $a = 2~m/s^2$
(b) $a = 4~m/s^2$

#### Work Step by Step

The mass of the object is 0.500 kg. So,
(a) $F = ma$
$a = \frac{F}{m}$
$a = \frac{1~N}{0.500~kg}$
$a = 2~m/s^2$
(b) $F = ma$
$a = \frac{F}{m}$
$a = \frac{2~N}{0.500~kg}$
$a = 4~m/s^2$