The particle moves with constant speed in a circular path, so its acceleration vector always points toward the circle's center.
At time 
, the acceleration vector has direction 
such that
which indicates the particle is situated at a point on the lower left half of the circle, while at time 
the acceleration has direction 
such that
which indicates the particle lies on the upper left half of the circle.
Notice that 
. That is, the measure of the major arc between the particle's positions at and is 270 degrees, which means that 
is the time it takes for the particle to traverse 3/4 of the circular path, or 3/4 its period.
Recall that
where 
is the radius of the circle and 
is the period. We have
and the magnitude of the particle's acceleration toward the center of the circle is
So we find that the path has a radius of
Did you try googling it lol thats what i do if its a problem like that. sometimes there are websites that answer it you just have to look really hard
The amount of friction depends on the force pushing the surfaces together. If this force increases, the hills and valleys of the surfaces can come into closer contact. The close contact increases the friction between the surfaces.
It is a reflecting telescope and a compound microscope. I know this for sure
