Re: What will happen if I push away from an object having the same mass as me?

Question:
What will happen if I push away from an object having the same mass as me? I mean this in space. I know that this has to do with Newton's third law. I also understand what would happen if the objects in space were of different masses. What I don't understand is what if they were the same! I don't know if they wouldn't move at all.....or if both of them would barely move but in equal and opposite directions.

Answer:
The short answer is: they would move apart in equal and opposite directions.

Let me explain how you could have figured this out on your own.

You can think about the answer to this problem using what you intuitively know about physics so far. For example, you know that if you push away from an object, and there’s nothing behind you to get in the way, you will move away from the object.And you know that the object will move away from you.

Look at the pictures I’ve drawn. In picture #1a, the astronaut is going to push away from a small object.As you would expect, the small object moves away quickly (#1b). This is because it is so much smaller than the astronaut. The arrows show the relative speed of the two objects after the push.

In picture #2a, we have the situation you are curious about: two astronauts with the same mass. They push away from each other, and move in opposite directions at the same speed (#2b).

In the last example (#3a), we have the astronaut trying to push away from a satellite (which is a lot heavier). The satellite is so much more massive, it’s a little like pushing away from a brick wall! And when you push away from a brick wall, you clearly move away, and the wall hardly moves at all. The satellite has its mass holding it in place, and may move only a little tiny bit if pushed against (#3b).

See if this makes sense.If you push away a small object, it moves away quickly, but you still move a little. If you push away a large object, you move away quickly, and it moves just a little. So, if you push something the same size as you, then the answer has to be somewhere in between, right?

As an experiment, find another person about the same weight as you, and both of you put on roller skates. Slowly and carefully push away from each other and see what happens. Do either of you move?