Given :
Two astronauts, one of mass 64 kg and the other 86 kg , are initially at rest together in outer space.
To Find :
How far apart are they when the lighter astronaut has moved 10 mm.
Solution :
Since, there is no force in space.
So, applying conservation of momentum :
![64v_1 + 86v_2 = 0\\\\v_2 = - (32)/(43)v_2](https://img.qammunity.org/2021/formulas/physics/college/g4hpnbtvfm33znomzczfp13rz5ikajean1.png)
We know, distance travelled by smaller astronaut is :
![10 = v_1t](https://img.qammunity.org/2021/formulas/physics/college/pvtcetio2loeh5e8r4juth8nb1z49bgw0q.png)
For bigger astronaut distance travelled :
![v_2t = -(32)/(43)(v_1t)\\\\v_2t = -(32)/(43)* 10\\\\v_2t = -7.44\ mm](https://img.qammunity.org/2021/formulas/physics/college/1azsjgap7h5i5bqys96bvy9irwv1ge38ee.png)
Therefore, they are ( 10 + 7.44 ) = 17.44 mm apart from each others.
Hence, this is the required solution.