I have listed my answer but the program sais why they are wr

I have listed my answer but the program sais why they are wrong? Please correct me.

(a) Assume the station is initially not rotating, and assume that the entire mass of the space station is concentrated in the outer ring. Also assume that the crew is initially on the outer rim. Rockets on the outside of the outer rim are fired tangentially to get the station spinning up to a speed such that the crew experiences a centripetal acceleration equal to g. What is the total angular momentum of the space station (plus crew) when it is up to maximum speed?

Answer: 7.31E8 kg*m^2/s
Your response differs from the correct answer by more than 100%.

(b) How much work is done to get the space station spinning?
Answer: 3.34E8 J
Your response differs from the correct answer by more than 100%. why?????

(c) How long must the rockets be fired if there are 2 rockets, and each exerts a thrust of 50 N?
Answer: 63591. s is my answer but my response differs from the correct answer by more than 100%. why????

(d) The rockets are no longer thrusting. The entire crew moves to the very center of the space station. What acceleration does an ant experience on the outer rim?

Answer:214.38 m/s^2

Your response differs from the correct answer by more than 100%. Why???

Solution

a)

Total moment of inertia

I =I_station +I_crew =Mr² +250mr² =(4.05*10⁴)*115²+250*80*115²

I=8*10⁸kg-m²

angular velocity

W=sqrt[a/r] =sqrt[9.8/115]=0.292 rad/sec

Angular momentum

L=IW =(8*10⁸)*0.292 =2.336*10⁸kg-m²/s

b)

work done to get the space station spinning

W=KE_rot =(1/2)IW² =(1/2)(8*10⁸)*0.292²

W=6.82*10⁷ J

c)

Torque

T=Fr =(2*50)*115 =11500 N-m

angular acceleration

alpha =T/I =11500/8*10⁸

alpha =1.437*10^-5 rad/s²

time taken by the rockets to be fired is

t=W/alpha =0.292/(1.437*10^-5)

t=20316 s

d)

By Conservation of angular momentum

L_i=L_f

I_iW_i =I_fW_f

2.336*10⁸ =(4.05*10⁴*115²)*W_f

W_f =0.436 rad/s

acceleration

a=W_f²r =0.436²*115 =21.87 m/s²