Astronaut throwing bag and rock: momentum conservation

[Dmt669]

Please help

An astronaut , 80 KG, is carrying a bag which is 20 KG, walking at a speed of 2 M/S toward a station, He throw the 20 KG bag forward at 6 M/s, what is his final velocity and direction(away from station, toward station)

heres another one

an astronaut is walking at .15 M/S toward a station, he wants to stop, he throws a 2.5 KG rock toward the station , what does a speed of the rock have to be in order for him to stop, thanks

 

[Galileo]

The total momentum is always conserved.
Before the astronaut throws the rock, the total momentum is:
$$p=(m_a+m_b)v$$
where $m_a$ is the mass of the astronaut and $m_b$ the mass of the bag.
What is the total momentum after the astronaut has thrown the rock?

Same reasoning applies to the second question.

 

[dextercioby]

Galileo,u mixed the bag with the rock and hence the problems

Now,after the precious indications given,which could have been put into 4 simple words "APPLY CONSERVATION OF MOMENTUM",what are the results...?

Daniel.

 

[Curious3141]

Please help

An astronaut , 80 KG, is carrying a bag which is 20 KG, walking at a speed of 2 M/S toward a station, He throw the 20 KG bag forward at 6 M/s, what is his final velocity and direction(away from station, toward station)

heres another one

an astronaut is walking at .15 M/S toward a station, he wants to stop, he throws a 2.5 KG rock toward the station , what does a speed of the rock have to be in order for him to stop, thanks

Apply conservation of momentum, taking care to make sure the signs of the velocities are consistently applied. And show your thoughts and working first.

 

[Dmt669]

The total momentum is always conserved.
Before the astronaut throws the rock, the total momentum is:
$$p=(m_a+m_b)v$$
where $m_a$ is the mass of the astronaut and $m_b$ the mass of the bag.
What is the total momentum after the astronaut has thrown the rock?

Same reasoning applies to the second question.

i am having trouble finding the final velocity of the astronaut though

 

[Curious3141]

i am having trouble finding the final velocity of the astronaut though

In the first problem, take the direction of travel toward the station as positive.

What is the initial momentum of the astronaut-bag combo ?

What is the final momentum of the bag ?

Therefore what is the final momentum of the astronaut ? Hence what is the final velocity of the astronaut ?

Do the second problem with the same basic principles.

 

[Dmt669]

In the first problem, take the direction of travel toward the station as positive.

What is the initial momentum of the astronaut-bag combo ?

What is the final momentum of the bag ?

Therefore what is the final momentum of the astronaut ? Hence what is the final velocity of the astronaut ?

Do the second problem with the same basic principles.

WHAT Formula should I use

 

[Curious3141]

WHAT Formula should I use

Do you mean to say that you don't know the definition of momentum ? You've never learned $p = mv$ ?

 

[Dmt669]

is the answer to the first [roblem 4 m/s backwards

 

[Curious3141]

is the answer to the first [roblem 4 m/s backwards

That is not correct. Show the working please.