Answer:
yes friction is needed hope this helps might of been to long tho
Answers:
a) 
b) 
c) 
Explanation:
We have the following data:
is the spring constant
is the amplitude of oscillation
is the velocity of the block when
Now let's begin with the answers:
<h3>a) Mass of the block</h3>
We can solve this by the conservation of energy principle:
(1)
Where:
is the initial potential energy
is the initial kinetic energy
is the final potential energy
is the final kinetic energy
Then:
(2)
Isolating
:
(3)
(4)
(5)
<h3>b) Period</h3>
The period
is given by:
(6)
Substituting (5) in (6):
(7)
(8)
<h3>c) Maximum acceleration</h3>
The maximum acceleration
is when the force is maximum
, as well :
(9)
Being 
Hence:
(10)
Finding
:
(11)
(12)
Finally:

This is a conservation of momentum problem! Here's how to do it:
Sphere is that the circular objects in the two dimensional space (1) circle
(2) disk. Two dimensional space is a set of points and the distance of that point,The two points of Sphere that length and center.
Sphere can constructed as the named of surface form circle about any diameter. circle is the special type of the revolution replacing the circle,
sphere is the distance r is the radius of the ball and circle is the center of mathematical ball,as the center and the radius of the sphere is to respectively.
The ball and sphere has not be maintained mathematical references as a solid references. A sphere of any radius is centered at the number of zero.
Answer:
10 :)
You have to divide the difference of speed and divide it by the time. So 100-20 would be 80, and if you divide that by 8 it would be 10.
Hope this helps.