SOLUTION: A satellite leaves earth at 3km/sec. After 100days earth sends out a radio signal traveling at 3(10)^5 km/sec. How long will it take the radio signal to reach the satellite? THA

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Question 27198: A satellite leaves earth at 3km/sec. After 100days earth sends out a radio signal traveling at 3(10)^5 km/sec. How long will it take the radio signal to reach the satellite? THANK YOU!!
I converted 100days into seconds (144000sec) and found the distance traveled to be 420000km. Do I even need to do that? thanks again
Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website!
I want to start my stopwatch at a time and I want to stop my
stopwatch at when the signal catches up with the satellite.
When should be?
I want it to be when the signal is sent from Earth because both the satellite
and the signal are active then.
Where is the satellite when the signal is sent? It has travelled

r[sat] = 3 km/sec
t[sat] = 100 days x 24 hrs/day x 60 min/hr x 60sec/min = 8,640,000 sec

in km
That's the headstart the satellite has.
Now start the stopwatch. It's t[0]
For the signal:

t[sig] is going to be the same as t[sat] because t[1] - t[0] is the same
for both of them, so just call it t.

d[sig] is equal to d[sat] + the headstart the satellite has

for the satellite
(t runs from t[0] to t[1])
substitute in

subtract 3*t from both sides and rearrange

t = 86.3 sec approximately
There are lots of chances for error, but I think my approach is OK