An unfortunate astronaut loses his grip during a spacewalk and finds himself floating away from the space station, carrying only a rope and a bag of tools. first he tries to throw a rope to

So i think that the question you are asking is the one of the exercise that says that the rope is very short and throws his bag also and you need to find the final speed of the bag tools. Well given the data we can use this next formulas to do this. First we are talking about conserve momentum: So we use a formula with the data like this:
(135 + 13.0)kg * 1.50m/s = 135kg * V + 13.0kg * v 
As we want V = 0; then 
minimum v = 148kg * 1.50m/s / 13.0kg = 17.1 m/s
I hope is what you were looking for