Answer
(a) $a = 18.3~m/s^2$
(b) $a = 2.29~m/s^2$
Work Step by Step
(a) $\sum F = ma$
$F + mg~sin(\theta) - mg~cos(\theta)~\mu_k = ma$
$a = \frac{F + mg~sin(\theta) - mg~cos(\theta)~\mu_k}{m}$
$a = \frac{120.0~N+(10.0~kg)(9.80~m/s^2)~sin(55.0^{\circ})-(10.0~kg)(9.80~m/s^2)~cos(55.0^{\circ})(0.300)}{10.0~kg}$
$a = 18.3~m/s^2$
(b) $\sum F = ma$
$F - mg~sin(\theta) - mg~cos(\theta)~\mu_k = ma$
$a = \frac{F - mg~sin(\theta) - mg~cos(\theta)~\mu_k}{m}$
$a = \frac{120.0~N-(10.0~kg)(9.80~m/s^2)~sin(55.0^{\circ})-(10.0~kg)(9.80~m/s^2)~cos(55.0^{\circ})(0.300)}{10.0~kg}$
$a = 2.29~m/s^2$
