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

Gravitational potential energy can be described as m*g*h (mass times gravity times height).
Originally,
15kg * 9.8m/s^2 *0.3 m = 44.1 kg*m^2/s^2 = 44.1 Joules.
After it is moved to a 1m shelf:
15kg * 9.8m/s * 1 = 147 kg*m^2/s^2= 147 Joules.
To find how much energy was added, we subtract final energy from initial energy:
147 J - 44.1 J = 102.9 Joules.
Answer:
The mass of the earth, 
Explanation:
It is given that,
Time taken by the moon to orbit the earth, 
Distance between moon and the earth,
We need to find the mass of the Earth using Kepler's third law of motion as :




So, the mass of the earth is
. Hence, this is the required solution.