Astronaut
Catch
A GIF Animation
Imagine that you are hovering next to the space shuttle in
earth-orbit and your buddy of equal mass who is moving 4 m/s (with
respect to the ship) bumps into you. If she holds onto you, then how
fast do the two of you move after the collision?
A question like this involves momentum principles. In any
instance in which two objects collide and can be considered isolated
from all other net forces, the conservation of momentum principle can
be utilized to determine the post-collision velocities of the two
objects. Collisions between objects are governed by laws of momentum
and energy. When a collision occurs in an isolated system, the total
momentum of the system of objects is conserved. Provided that there
are no net external forces acting upon the two astronauts, the
combined momentum of the two astronauts before the collision equals
the combined momentum of the two astronauts after the collision.
The mathematics of this problem is simplified by the fact that
before the collision, there is only one object in motion and after
the collision both objects have the same velocity. That is to say, a
momentum analysis would show that all the momentum was
concentrated in the moving astronaut before the collision. And
after the collision, all the momentum was the result of a single
object (the combination of the two astronauts) moving at an
easily predictable velocity. Since there is twice as much mass in
motion after the collision, it must be moving at one-half the
velocity. Thus, the two astronauts move together with a velocity of 2
m/s after the collision.
For more information on physical descriptions of motion,
visit
The
Physics Classroom. Specific information is available there on the
following topics:
This page was created by
Tom
Henderson of
Glenbrook South
High School.
Comments and suggestions can be sent by e-mail to
Tom
Henderson.
A hearty thanks is due to lab assistant Bryce Mautner for her
assistance with the graphics and GIF animation.
This page last updated on 6/6/97.