Answer:
 T/√8 
Explanation:
From Kepler's law, T² ∝ R³ where T = period of planet and R = radius of planet.
For planet A, period = T and radius = 2R.
For planet B, period = T' and radius = R.
So, T²/R³ = k
So, T²/(2R)³ = T'²/R³
T'² = T²R³/(2R)³ 
T'² = T²/8
T' = T/√8 
So, the number of hours it takes Planet B to complete one revolution around the star is T/√8 
 
        
             
        
        
        
All of Dina's potential energy Ep is converted into kinetic energy Ek so Ep=Ek, where Ep=m*g*h and Ek=(1/2)*m*v². m is the mass of Dina, h is the height of ski slope, g=9.8 m/s² and v is the maximal velocity. 
So we solve for v:
m*g*h=(1/2)*m*v², masses cancel out,
g*h=(1/2)*v², we multiply by 2,
2*g*h=v² and take the square root to get v
√(2*g*h)=v, we plug in the numbers and get:
v=9.9 m/s. 
So Dina's maximum velocity on the bottom of the ski slope is v=9.9 m/s.
        
                    
             
        
        
        
Um what are the ten objects..?
        
             
        
        
        
To solve this problem it is necessary to apply the kinematic equations of motion.
By definition we know that the position of a body is given by

Where
 Initial position
 Initial velocity
a = Acceleration
t= time 
And the velocity can be expressed as,

Where,

For our case we have that there is neither initial position nor initial velocity, then

With our values we have 
, rearranging to find a,



Therefore the final velocity would be



Therefore the final velocity is 81.14m/s
 
        
             
        
        
        
Answer:
199.0521 Will be the answer