Answer:
a.=4.78 m/s2
b. the thread will remain vertical
Step-by-step explanation:
a.
For jet acceleration as you know,
Weight due to gravity given as
F= w =mg
and body movement with acceleration as
F= ma





Its acceleration of plane
b.
For planes attaining constant velocity
a = 0 and tan∅ = 0
so Ф = 0
hence the thread will be remain vertical