Explanation:
The position vector r:

The velocity vector v:

The acceleration vector a:



The center of mass is given with this formula:

Velocity is:

So, for the velocity of the center of mass we have:

In our case it is:
Answer:
<em><u>True:</u></em> because when u look thru a telescope you are making an observation
Explanation:
<span>Make the surfaces smoother. Rough surfaces produce more friction and smooth surfaces reduce friction
Lubrication is another way to make a surface smoother
Make the object more streamlined
Reduce the forces acting on the surfaces
<span>Reduce the contact between the surfaces.</span></span>