To solve this problem we will apply the concepts related to the balance of forces. Said balance will be given between buoyancy force and weight, both described as derived from Newton's second law, are given as
Buoyancy force
Here,
V = Volume
=Density of air
g = Acceleration due to gravity
Weight
m = mass
g = Gravity
Our values are given as,
Then,
Replacing,
Now net force is ,
Mass of the sphere is
Now acceleration of the sphere is
Therefore the acceleration of the sphere as it falls through water is 
Answer:
Explanation:
In order to solve this problem we need to make a free body diagram of the book and the forces that interact on it. In the picture below you can see the free body diagram with these forces.
The person holding the book is compressing it with his hands, thus exerting a couple of forces of equal magnitude and opposite direction with value F.
Now the key to solving this problem is to analyze the equilibrium condition (Newton's third law) on the x & y axes.
To find the weight of the book we simply multiply the mass of the book by gravity.
W = m*g
W = 1.3[kg] * 9.81[m/s^2]
W = 12.75 [N]
Answer : 6.022• 10^23 atoms of potassium
