# Homework Help: Making Connections-I clearly do not know how

1. Jul 11, 2009

### IAmLost

Making Connections--I clearly do not know how

During a space walk, an astronaut becomes stranded a short distance from the spacecraft. Explain how the astronaut could solve the problem by applying conservation of momentum to return safely to the spacescraft. State any assumptions needed for your solution to work.

okies wellll....i tried using the m1V1i+m2v2i=m1v1f+m2v2f...buuut im soo confused and i dont understand wthhheck im doinnnggg someone plz help me

2. Jul 11, 2009

### Feldoh

Re: Making Connections--I clearly do not know how

Think about it, what would astronauts have with them on a space walk, and how would that help them?

3. Jul 11, 2009

### IAmLost

Re: Making Connections--I clearly do not know how

um...some velocity detector? or a camera...a watch?...oorr a gps..then they cud just look ther
i seriously dunno....i guess a watch cud help to find their time?..buu how does that help?
lol u can tell by now that i am a lost cause :P

4. Jul 11, 2009

### cepheid

Staff Emeritus
Re: Making Connections--I clearly do not know how

All of the objects you mention have mass. How could an astronaut use something with mass to get himself moving, using the principle of conservation of momentum? Hint: how does a rocket work in the first place?

5. Jul 11, 2009

### IAmLost

Re: Making Connections--I clearly do not know how

ommggg..likke that thingie they use that pushes them forwarddd...aha..soo..now that i know that how does that help me with the momentum equation? wuut do i do now? what am i comparin the astronaut to? and how does that help the guy get back to his spaceship :S

6. Jul 11, 2009

### diazona

Re: Making Connections--I clearly do not know how

Don't bother with any equations. This isn't a mathematical problem, it's just about physical intuition.

Think about this: the astronaut started out with zero momentum (i.e. not moving). Conservation of momentum means that the net total momentum of the astronaut and all the stuff he's carrying remains at zero. Now, if the astronaut is going to get back to his spaceship, he needs to have some momentum toward the spaceship. So how could the astronaut get some momentum toward the spaceship, without the net total momentum of him and his stuff changing from zero?

7. Jul 12, 2009

### IAmLost

Re: Making Connections--I clearly do not know how

thank you thank you thankkk youu for everyones time and help
i get it now:D

but i have some more lol;P

if there was a car and SUV in a collision, and the speed limit was 80 km/h, and mass of suv is twice mass of the car. both guys came to a stop at the location of the inital impact. both guys survived and claimed to be travelling at the speed limit...LIES... it is obvious that one car is lying, use numercial data to explain why...
umm ye...this is wut i thot, but it really doesnt make sense :S

i talked about the conservation of momentum and how the kinetic energy of the inital was greater than the final (since the final velocities were 0) and i said how it was a completely inelastic collision,and yee...but i dunno if wut im talkin bout is right...i just need someone to confirm or correct my answer thanks:D

oh and also...lol...if they were telling the truth and were both going at the speed limit, but still crashed head-on...how would it be different?

EDIT: i get the first part of the question, (they were lying because if they were telling the truth, the masses should have been equal, which they weren't)...buut i dunno what wud happen if they were both telling the truth....if anyone can help plz and thanks:D

EDIT #2: nvmm got itt thx:D

Last edited: Jul 12, 2009