Explain why space junk is a hazard to an astronats or spacecraft

Space junk is travelling so fast that a collision with an astronaut or a spacecraft could be disastrous.

Explanation:

Space junk orbits the Earth at speeds of about 28 000 km/h.  

That's so fast that even an orbiting fleck of paint has enough kinetic energy to cause impact craters on the surface of a spacecraft. They are even more dangerous to an astronaut on a space walk.

Much of the space debris is larger and more dangerous than a fleck of paint.

One rough estimate of the amount of space debris is

      Size                Number of objects

< 1 cm                        200 000 000

1 cm to 10 cm                   700 000

> 10 cm                                 30 000

Satellites, etc.                       18 000

The chances of collision are small, but any collision can be disastrous.

plasma is the state of matter where the substance is ionized and has no definite shape or volume. the fact of being ionized makes the substance a good electrical conductor.