C. hydrogen accreted onto a white dwarf from a close companion rapidly fuses to helium, releasing a large amount of energy.
The accreted material, composed mainly of hydrogen, is compacted on the surface of the white dwarf due to the intense gravitational force on that place. As material accumulates, The white dwarf becomes increasingly hot, until it reaches the critical temperature for ignition of nuclear fusion.
 
        
             
        
        
        
Answer:
14 m/s
Explanation:
The motion of the book is a free fall motion, so it is an uniformly accelerated motion with constant acceleration g=9.8 m/s^2 towards the ground. Therefore we can find the final velocity by using the equation:

where
u = 0 is the initial speed
g = 9.8 m/s^2 is the acceleration
d = 10.0 m is the distance covered by the book
Substituting data, we find

 
        
             
        
        
        
Answer:
Net force is Zero.
Explanation:
If all forces that are equal and opposite are exerted on an object the resulting force will be Zero. 
 
        
                    
             
        
        
        
Answer:
Distance, d = 778.05 m                           
Explanation:
Given that,
Force acting on the car, F = 981 N
Mass of the car, m = 1550 kg
Initial speed of the car, v = 25 mi/h = 11.17 m/s
We need to find the distance covered by car if the force continues to be applied to the car. Firstly, lets find the acceleration of the car:

Let d is the distance covered by car. Using second equation of motion as :

So, the car will cover a distance of 778.05 meters.
 
        
             
        
        
        
complete question:
A child bounces a 60 g superball on the sidewalk. The velocity change of the superball is from 22 m/s downward to 15 m/s upward. If the contact time with the sidewalk is 1/800 s, what is the magnitude of the average force exerted on the superball by the sidewalk
Answer:
F = 1776  N
Explanation:
mass of ball = 60 g = 0.06 kg
velocity of downward direction = 22 m/s = v1
velocity of upward direction = 15 m/s = v2
Δt = 1/800 = 0.00125 s
Linear momentum of a particle with mass and velocity is the product of the mass and it velocity. 
p = mv
When a particle move freely and interact with another system within a period of time and again move freely like in this scenario it has a definite change in momentum. This change is defined as Impulse . 
I = pf − pi = ∆p
F =  ∆p/∆t  =  I/∆t
let the upward velocity be the positive 
Δp =  mv2 - m(-v1)
 Δp =  mv2 - m(-v1)
Δp = m (v2 + v1)
Δp = 0.06( 15 + 22)
Δp = 0.06(37)
Δp = 2.22 kg m/s
∆t  = 0.00125 
F =  ∆p/∆t
F =  2.22/0.00125
F = 1776  N