Answer
a) See the detailed answer below.
b) $10.38\;\rm m/s^2$
Work Step by Step
a) A 15,000 N-air plane is rolling down a road tilted at 15$^\circ$ above the horizontal. The friction between the road and the plane\s tires here is assumed to be negligible.
Its engine is providing a force of 12,000 N parallel to the surface of the tilted road.
Find its acceleration.
b)
$$\sum F_x=12000+15000\sin15^\circ=ma_x$$
Recall that $m=\dfrac{F_G}{g}$
Thus,
$$ 12000+15000\sin15^\circ=\dfrac{F_G}{g}\;a_x$$
$$a_x= \dfrac{g}{F_G}\left[ 12000+15000\sin15^\circ\right]=\dfrac{9.8}{15000}\left[ 12000+15000\sin15^\circ\right] $$
$$a_x=\color{red}{\bf 10.38}\;\rm m/s^2$$
