Answer:
2
Explanation:
A rigid body is not elastic.
i.e. it does not change shape.
Acceleration of the ball is 
Explanation:
The acceleration of the ball can be found by using Newton's second law of motion, which states that the net force acting on an object is equal to the product between the mass of the object and its acceleration:

where
F is the net force
m is the mass
a is the acceleration
For the ball in this problem, we have
m = 0.50 kg (mass)
F = 25 N (force)
thereofre, the acceleration of the ball is

Learn more about Newton's second law:
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The law of conservation of energy states that in a closed or isolated system, the amount of energy remains constant because energy can neither be created or destroyed. It can only be transferred from one form into another. This applies to all forms of energy.
Answer:
39.2m/s
Explanation:
The potential energy the book has right before it falls is equal to the kinetic energy in falling.
PE = KE
mgh = (1/2)mv
2gh=v
v=(2)(9.81)(2)
v=39.24m/s